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1.
Antiserum generated in a horse against testosterone conjugated to bovine serum albumin (BSA) was administered to six lighthorse mares (androgen-immunized mares) 1 to 3 d before a prostaglandin-induced estrus and twice again at 2-d intervals. Six control mares were administered antiserum generated against BSA on the same schedule. Relative to testosterone, cross-reactivities of other steroids with the testosterone antiserum were (%): dihydrotestosterone, 52; 5 alpha-androstane-3 alpha,17 beta-diol, 8.6; androst-4-ene-3,17-dione, 1.2; and all others tested less than .1. Tritiated testosterone binding in plasma increased (P less than .01) in androgen-immunized mares within 1 h and remained elevated (P less than .01) relative to controls for greater than 21 d. There was no effect (P greater than .10) of passive immunization against androgen on interval to estrus after prostaglandin injection, duration of estrus, ovarian volume, number of palpable follicles or follicular volume during estrus. In contrast, concentrations of luteinizing hormone (LH) were higher (P less than .05) in androgen-immunized mares than in control mares during estrus and early diestrus. Concentrations of follicle stimulating hormone (FSH) and progesterone at those times were not affected (P greater than .10). From these data, we conclude that androgens in the mare during estrus may be involved with the regulation of LH secretion. In contrast, no involvement with FSH secretion was apparent under these short-term conditions.  相似文献   

2.
Effects of testosterone propionate (TP) treatment on plasma concentrations of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) before and after an injection of gonadotropin releasing hormone (GnRH) were studied using ovariectomized cows and pony mares. An initial injection of GnRH (1 microgram/kg of body weight) was followed by either TP treatment or control injections for 10 (cows) or 11 (ponies) d. A second GnRH injection was administered 1 d after the last TP or oil injection. Concentrations of LH and FSH were determined in samples of plasma taken before and after each GnRH injection. Control injections did not alter the response to GnRH (area under curve) nor the pre-GnRH concentrations of LH and FSH in ovariectomized cows or ponies. Testosterone treatment increased (P less than .01) the FSH release in response to GnRH in ovariectomized mares by 4.9-fold; there was no effect in cows, even though average daily testosterone concentrations were 59% higher than in pony mares. Testosterone treatment reduced the LH release in response to GnRH by 26% in ovariectomized mares (P less than .05) and by 17% in ovariectomized cows (P approximately equal to .051). These results are consistent with a model that involves ovarian androgens in the regulation of FSH secretion in the estrous cycle of the mare, but do not support such a model in the cow.  相似文献   

3.
Eight seasonally anestrous mares were administered intravaginal polyurethane sponges on December 15 and then weekly thereafter until February 1. Control mares received no sponges or genital contact. Sponge insertion caused an immediate surge in follicle-stimulating hormone (FSH) concentrations in jugular plasma in 50% of treated mares whereas no control mares had surges in FSH (P less than .05). The effect of treatment on luteinizing hormone (LH) concentrations was much less dramatic and only three treated mares appeared to have positive responses. Sponge-treated mares exhibited positive responses in FSH concentrations 11 times out of 32 mare-days and control mares zero out of 28 (P less than .05). The magnitude of the FSH response decreased rapidly with successive responses. Sponge insertion induced estrus in four of eight treated mares; no control mares exhibited estrus (P less than .05). Sponge insertion also increased ovarian size and the incidence of large follicles. When all mares were fed altrenogest for 14 d beginning February 1, there was no beneficial effect of sponge treatment on number of mares exhibiting estrus or on pregnancy rate. These data confirm earlier speculations that sponge treatment causes surges in gonadotropins and increased ovarian size in approximately 50% of anestrous mares. However, sponge treatment does not appear to provide a practical means of preparing mares for progestogen synchronization during the nonbreeding season.  相似文献   

4.
OBJECTIVE: To evaluate gonadotropin secretion and ovarian function after administration of deslorelin acetate to induce ovulation in mares. DESIGN: Randomized controlled trial. ANIMALS: 16 healthy mares with normal estrous cycles. PROCEDURE: 8 control mares were allowed to ovulate spontaneously, whereas 8 study mares received deslorelin to induce ovulation when an ovarian follicle > 35 mm in diameter was detected. Follicle development and serum concentrations of gonadotropins were monitored daily during 1 estrous cycle. Pituitary responsiveness to administration of gonadotropin-releasing hormone (GnRH) was evaluated 10 days after initial ovulation. RESULTS: Interovulatory intervals of mares treated with deslorelin (mean +/- SD, 25.6 +/- 2.6 days) were longer than those of control mares (22.9 +/- 1.8 days). Diameter of the largest follicle was significantly smaller during 2 days of the diestrous period after ovulation in deslorelin-treated mares than in control mares. Concentrations of follicle-stimulating hormone (FSH) were lower in deslorelin-treated mares on days 5 through 14 than in control mares. Concentrations of luteinizing hormone were not different between groups during most of the cycle. Gonadotropin release in response to administration of GnRH was lower in mares treated with deslorelin acetate than in control mares. CONCLUSIONS AND CLINICAL RELEVANCE: Administration of deslorelin was associated with reduction in circulating concentrations of FSH and gonadotropin response to administration of GnRH during the estrous cycle. Low concentration of FSH in treated mares may lead to delayed follicular development and an increased interovulatory interval.  相似文献   

5.
The present experiment characterized the pituitary responsiveness to exogenous GnRH in the first 10 d after ovulation following commercially available deslorelin acetate implantation at the normal dosage for hastening ovulation in mares. Twelve mature, cyclic mares were assessed daily for estrus and three times weekly for ovarian activity starting May 1. Mares achieving a follicle at least 25 mm in diameter or showing signs of estrus were checked daily thereafter for ovarian characteristics. When a follicle >30 mm was detected, mares were administered either a single deslorelin acetate implant or a sham injection and then assessed daily for ovulation. On d 1, 4, 7, and 10 following ovulation, each mare was challenged i.v. with 50 microg GnRH, and blood samples were collected to characterize the LH and FSH responses. The size of the largest follicle on the day of treatment did not differ (P = 0.89) between groups. The number of days from treatment to ovulation was shorter (P < 0.001) by 2.0 d for the treated mares indicating a hastening of ovulation. The size of the largest follicle present on the days of GnRH challenge was larger in the treated mares on d 1 (P = 0.007) but smaller on d 10 (P = 0.02). In addition, the interovulatory interval was longer (P = 0.036) in the treated mares relative to controls by 4.4 d. Concentrations of FSH in plasma of the treated mares were lower (P < 0.05) than control concentrations from d 3 to 12; LH concentrations in the treated mares were lower (P < 0.05) relative to controls on d 0 to 5, d 7, and again on d 20 to 23. Progesterone values were the same (P = 0.99) for both groups from 2 d before ovulation though d 23. There was an interaction of treatment, day, and time of sampling (P < 0.001) for LH and FSH concentrations after injection of GnRH. Both the LH and FSH responses were suppressed (P < 0.009) in the treated mares relative to controls on d 1, 4, and 7; by d 10, the responses of the two groups were equivalent. In conclusion, deslorelin administration in this manner increased the interovulatory interval, consistently suppressed plasma LH and FSH concentrations, and resulted in a complete lack of responsiveness of LH and FSH to GnRH stimulation at the dose used during the first 7 d after the induced ovulation. Together, these results are consistent with a temporary down-regulation of the pituitary gland in response to deslorelin administered in this manner.  相似文献   

6.
Three experiments were performed to test the following hypotheses: 1) stallions and/or progesterone-estradiol-treated geldings could serve as models for the effects of a single implant of the GnRH analog, deslorelin acetate, on LH and FSH secretion by mares; and 2) multiple implants of deslorelin acetate could be used as a means of inducing ovarian atrophy in mares for future study of the mechanisms involved in the atrophy observed in some mares after a single implant. In Exp. 1, nine light horse stallions received either a single deslorelin implant (n = 5) or a sham injection (n = 4) on d 0. In Exp. 2, 12 geldings received daily injections of progesterone on d -20 through -4, followed by twice-daily injections of estradiol on d -2 to 0. On the morning of d 0, geldings received either a single deslorelin implant (n = 6) or a sham injection (n = 6). Daily injections of progesterone were resumed on d 2 through 15. In Exp. 1, plasma LH and FSH were elevated (P < 0.05) in the treatment group relative to controls at 4, 8, and 12 h after implant insertion. In the treated stallions, FSH was decreased (P < 0.05) on d 3 to 13, and LH was decreased on d 6 to 13. In Exp. 2, plasma LH and FSH were elevated (P < 0.05) at 4,8, and 12 h after deslorelin implant insertion. Plasma LH was suppressed (P < 0.05) below controls on d 2 to 7, 9, and 11 to 15; plasma FSH was suppressed (P < 0.05) on d 4 to 15. In Exp. 3, 21 mares were used to determine whether multiple doses of deslorelin would cause ovarian atrophy. Mares received one of three treatments: 1) sham injections; 2) three implants on the first day; or 3) one implant per day for 3 d (n = 7 per group). Treatment with multiple implants increased (P < 0.05) the interovulatory interval by 14.8 d and suppressed (P < 0.01) LH and FSH concentrations for approximately 25 d; no mare exhibited ovarian atrophy. In conclusion, after an initial short-term increase in LH and FSH secretion, deslorelin implants caused long-term suppression of both gonadotropins in stallions as well as in geldings treated with progesterone and estradiol to mimic the estrous cycle. It is likely that either of these models may be useful for further study of this suppression in horses. Although multiple implants in mares suppressed gonadotropin secretion longer than a single implant, the lack of ovarian atrophy indicates that the atrophy observed after a single implant in previous experiments was likely due to the susceptibility of individual mares.  相似文献   

7.
Ten stallions were used to determine if the stallion responds to administration of testosterone propionate (TP) with an increase in follicle stimulating hormone (FSH) secretion after administration of gonadotropin releasing hormone (GnRH) as has been previously observed for geldings and intact and ovariectomized mares. Five stallions were treated with TP (350 μg/kg of body weight) in safflower oil every other day for 11 days; control stallions received injections of safflower oil. The response to GnRH (1.0 μg/kg of body weight) was determined for all stallions before the onset of treatment (GnRH I) and at the end of treatment (GnRH II). Blood samples were also withdrawn daily from 3 days prior to treatment through GnRH II. Treatment with TP decreased (P<.10) concentrations of FSH in daily blood samples. However, treatment with TP did not affect (P>.10) the GnRH-induced secretion of FSH. Concentrations of luteinizing hormone (LH) decreased (P<.05) in daily blood samples averaged over both groups of stallions and were lower (P<.10) in TP-treated stallions than in controls during the latter days of treatment. We conclude that TP administration to stallions does not alter the FSH response to GnRH as has been observed for geldings and for mares of several reproductive states.  相似文献   

8.
Two homologous radioimmunoassays for bovine follicle stimulating hormone (bFSH) were utilized in comparing the differential regulation of FSH and luteinizing hormone (LH) in response to ovariectomy or administration of gonadal steroids in cattle. There appeared to be significant LH cross-reactivity in one of the bFSH systems (bFSH-HS-2-17), but not in the other (bFSH-BP3). Concentrations of FSH in plasma measured by these two systems suggested both qualitative and quantitative differences. Following ovariectomy in heifers, LH concentrations in plasma were increased by 7.5 h, while FSH (measured in the bFSH-BP3 system) was not significantly elevated until 18 h. Administration of 200 micrograms of estradiol-17 beta to ovariectomized heifers inhibited levels of FSH in plasma but large doses of testosterone (100 mg), androstenedione (400 mg) and dihydrotestosterone (800 mg) had no effect. Similarly, LH was not affected by the androgens, while estradiol induced LH surges, leading to increased mean LH concentrations. In contrast to the results in heifers, LH concentrations in plasma from steers were inhibited by administration of androgens as well as by estradiol. In steers, FSH (bFSH-BP3) was marginally inhibited by estradiol and not at all by the androgens. Differences in the secretory patterns of FSH and LH also occurred in intact heifers during the estrous cycle. The 72-h period preceding estrus (follicular phase) was characterized by rapidly declining serum progesterone concentrations, followed by concurrent increases in both LH and estradiol. The circulating levels of bFSH (BP3) tended to decline during this interval. Overall, during the estrous cycle, progesterone levels were positively correlated with bFSH-BP3 (r = .37) and negatively correlated with LH (r = -.39). The gonadotropins were not significantly related (r = -.15). These relationships are consistent with the concept that LH controls the final stages of follicular development in cattle and that FSH may exert only a permissive effect.  相似文献   

9.
Daily changes in the plasma progesterone concentrations were determined in eight mares treated with intramuscular injections of 250 μg cloprostenol, a prostaglandin analogue, followed five days later by 2500 I.U. human chorionic gonadotropin. A second cloprostenol injection was given 14 days after the first; the mares were then inseminated on the third and fifth day of the subsequent estrus and a second injection of human chorionic gonadotropin was administered on the fifth day. The onset of estrus following the second cloprostenol treatment was synchronized beginning three to four days after treatment in all eight mares. All eight ovulated, five mares conceived and only four foaled. Evaluation of the progesterone profiles provided reliable indicators of luteolysis, ovulation and luteal function. Decreasing plasma progesterone concentrations were associated with cloprostenol induced luteolysis or preceded spontaneous onset of estrus. The plasma progesterone concentrations increased consistently after ovulation, and in the pregnant mares, the progesterone concentrations remained high during the first month after insemination.  相似文献   

10.
Prostaglandin F2 alpha (PGF2 alpha) was injected on d 5, 8 or 11 postestrus in ewes to determine how stage of the estrous cycle would affect PGF2 alpha-induced changes in concentrations of ovarian and pituitary hormones and intervals to the onset of estrus and the preovulatory surge of luteinizing hormone (LH). Initial concentrations of progesterone and average values during the 12 h after PGF2 alpha were related positively to the day of cycle on which PGF2 alpha was administered. Patterns of decline in progesterone after injection of PGF2 alpha were similar among the 3 d. Concentrations of LH in plasma increased in a similar manner from 0 to 12 h in all ewes. After 12 h LH continued to increase, plateaued or declined in ewes treated on d 5, 8 or 11, respectively. Initial concentrations of follicle stimulating hormone (FSH) in plasma were related positively to day of treatment. After treatment with PGF2 alpha, FSH increased within 2 h on d 5 but declined by that time on d 8 or 11. Concentrations of estradiol following treatment did not vary with day. The onset of estrus and the preovulatory surge of LH occurred at 36 and 35, 40 and 45, and 48 and greater than 48 h in ewes treated on d 5, 8 or 11, respectively. It is concluded that: 1) the initial increase in LH is dependent on a decrease in plasma progesterone and 2) differences in patterns of secretion of gonadotropins before the preovulatory surge of LH might be caused by differences in progesterone or progesterone:-estradiol ratio when luteal regression is induced on different days of the estrous cycle.  相似文献   

11.
Thirteen crossbred boars were immunized at 1 mo of age against either testosterone-3-oxime-equine serum albumin (treated boars) or equine serum albumin (control boars) to test the hypothesis that active immunization against testosterone stimulates testicular growth and development in the prepubertal boar. All boars were injected with the appropriate antigen at 2, 3, 4, 5 and 6 mo of age and were slaughtered at 14 mo of age. Active immunization against testosterone resulted in an increase (P less than .05) in tritiated-testosterone binding by plasma within 60 d after the primary immunization; the degree of binding decreased by 6 mo but remained elevated (P less than .05) relative to controls through 12 mo of age. There was no effect of treatment on body weights through 12 mo of age. Concentrations of testosterone in plasma were higher (P less than .05) in testosterone-immunized boars than in controls; this increase was likely due to antibody binding rather than increased testosterone secretion because (1) concentrations of androgen in testicular parenchyma at slaughter were not altered by treatment and (2) plasma concentrations of estrogens were generally not affected by treatment. Concentrations of luteinizing hormone (LH) and follicle stimulating hormone (FSH) were markedly suppressed in testosterone-immunized boars during the time when concentrations of these gonadotropins were high in control boars (greater than 3 mo of age). In spite of suppression of average LH and FSH concentrations, testicular weights, daily sperm production rates and seminal characteristics were similar for the two groups of boars at slaughter. (ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

12.
Plasma estradiol concentration and follicular development were evaluated daily during the first postpartum estrus and the subsequent cycle of five foaling mares. For comparison, one estrous cycle was monitored in the same fashion for five nonparturient mares. The first postpartum estrous cycles were shorter but similar to non-pregnant cycles in ovarian steroid production and follicular activity. However, estradiol production from postpartum follicles was lower per mm follicular diameter than from follicles in nonpregnant cycles (p<0.05).  相似文献   

13.
The effects of compounded medroxyprogesterone acetate (MPA) on follicular activity and estrous behavior were evaluated. Eighteen cycling mares were assigned to one of three treatment groups. Mares in the MPA group (n = 6) were injected intramuscularly with 1,600 mg MPA (week 1), then 400 mg weekly for the next 5 weeks. Saline mares (n = 6) were injected intramuscularly weekly for 6 weeks. Altrenogest mares (n = 6) received 10 mL orally daily for 7 weeks. Mares were teased daily for 60 days and categorized as displaying estrous, diestrous, or neutral behavior. Transrectal ultrasound examinations were performed three times weekly, or daily when a 30-mm follicle was identified, until ovulation. Blood samples were harvested weekly for analysis of progesterone concentration and daily from days 14 to 23 for analysis of luteinizing hormone (LH) concentration. Mares treated with saline or MPA showed normal intervals of diestrus and estrus during the study. All altrenogest mares showed behavioral diestrus during treatment. All mares in the saline and MPA groups showed normal follicular development and ovulations. No altrenogest mares ovulated during treatment; four mares returned to estrus and resumed normal follicular development after treatment ceased. Progesterone analyses agreed with transrectal ultrasonographic ovarian activity for all mares. LH levels were lower for altrenogest-treated mares compared with MPA-treated and saline-treated mares during the treatment period. In conclusion, compounded MPA at dose rates and intervals used in this study was not effective in suppression of estrus, follicular development, or LH secretion in mares.  相似文献   

14.
Twenty ovariectomized pony mares were used to determine if dihydrotestosterone propionate (DHTP) administration, with or without estradiol benzoate (EB) pretreatment, would have the same effects on follicle stimulating hormone (FSH) and luteinizing hormone (LH) secretion as testosterone propionate (TP) administration. All mares were given an initial injection of gonadotropin releasing hormone (GnRH) to characterize their LH and FSH response, and then two groups of mares (n = 4/group) were administered EB (22 micrograms/kg of body weight), two groups were administered vehicle (safflower oil) and a fifth group was administered TP (175 micrograms/kg of body weight) daily for 10 days. Following a second injection of GnRH, one group of EB-treated mares and one group of oil-treated mares were administered DHTP (175 micrograms/kg of body weight) daily for 10 days; the other EB- and oil-treated mares were administered oil and the TP-treated mares were continued on the same dose of TP for 10 days. A final injection of GnRH was then given. Treatment with EB increased (P less than .01) concentrations of LH in daily blood samples and increased (P less than .05) the LH response to exogenous GnRH. Administration of TP or DHTP reduced (P less than .05) both daily LH concentrations and the LH response to exogenous GnRH. Concentrations of FSH in daily blood samples were reduced (P less than .05) and the FSH response to exogenous GnRH was increased (P less than .05) by administration of EB alone, DHTP alone or TP.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

15.
The effects of exogenous equine somatotropin (eST) administration on ovarian activity and plasma hormone levels were evaluated on horse and pony mares. The objectives of this study were to determine the effects of eST on follicular development and circulating concentrations of leutinizing hormone (LH), estradiol, progesterone, and insulin-like growth factor I (IGF-I) in cyclic horse and pony mares. Sixteen mares received daily injections (i.m.) of eST at a concentration of 25 micrograms/kg body weight on either Days 6 through 12 (Treatment A) or 13 through 19 (Treatment B) postovulation. In addition, contemporary mares were similarly given the carrier vehicle and served as controls (Treatments C and D). Blood samples were collected at 24-hr intervals and ultrasonographic evaluations were performed on the ovaries of each mare at 48-hr intervals beginning on the first day of treatment and ending either on the day of ovulation or 5 d postovulation. Circulating levels of insulin-like growth factor-I (IGF-I) were increased in treated mares by Day 3 post-treatment (P < 0.05). Also, mares in Treatment B exhibited a decrease in plasma estradiol concentrations (P < 0.05) when compared with control mares on Days 1 through 5 postovulation of the post-treated estrous cycle. In addition, circulating leutinizing hormone levels were different for mares in Treatment A compared with controls on Days--8 through--1 pre-ovulation (P < 0.05). All follicles present on the ovaries of each mare were measured and placed into one of five categories based on their diameter. Neither the mean number of follicles per size category > or = 8 mm in diameter nor the mean follicular diameter within each size category differed among treatment and control mares. However, eST treatment significantly increased the number of follicles < or = 7 mm on the ovaries of mares treated early in the estrous cycle when compared with control mares on Days 3 and 7 post-treatment and at the onset of standing estrus.  相似文献   

16.
Twelve long-term ovariectomized (OVX) pony mares were used to determine the effects of dexamethasone (DEX) or progesterone (PR) on concentrations of follicle stimulating hormone (FSH) and luteinizing hormone (LH) in daily blood samples and after administration of gonadotropin releasing hormone (GnRH). All mares were subsequently administered dihydrotestosterone (DHT) to determine if DEX or PR treatment altered the FSH or LH response to this androgen. Daily blood sampling was started on day 1. After a pretreatment injection of GnRH on day 5, four mares were administered DEX at 125 micrograms/kg of body weight (BW), four mares were administered PR at 500 micrograms/kg of BW and four mares were administered vehicle. Injections were given subcutaneously in vegetable shortening daily through day 14. After a second injection of GnRH on day 15, all mares were administered DHT in shortening at 150 micrograms/kg of BW. Injections of DHT were given daily through day 24. A final injection of GnRH was given on day 25. Treatment of mares with DEX 1) reduced (P less than .01) daily LH secretion and briefly increased (P less than .05) daily FSH secretion and 2) increased (P less than .01) the FSH response to exogenous GnRH. Treatment of mares with PR had no effect on daily LH secretion but increased (P less than .05) daily FSH secretion and increased (P less than .01) the FSH response to exogenous GnRH.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

17.
Stallion-like sexual behavior in mares is rare, except in association with ovarian tumors or hormonal treatments. The rarity of the phenomenon was confirmed in a recent 3-year study. The mean number of mares with detected stallion-like behavior, including mounting with thrusts, during an entire ovulatory season was 5.7 (17/3 years) in a herd averaging 105 mares (5% incidence/mare/season). From a total of 17 mountings of an estrous mare by another mare, 15 occurred when the mounting mare was in the follicular phase and two when in the early luteal phase. Plasma testosterone concentration on the day of mounting was higher (P < 0.01) in the mounting mares (17.7 ± 2.3 pg/ml) than in the standing mares (10.9 ± 0.5 pg/ml). No other deviation in the endocrine, behavioral, or morphologic aspects of the estrous cycle was observed. In another study, testosterone was assayed daily from 7 days before to 4 days after ovulation in seven mares during estrous cycles with no detected mare-on-mare mountings. Concentrations during the follicular phase were highest on the days corresponding to when mare-on-mare mounting was detected in the previous study. It is concluded that the rare occurrence of stallion behavior by untreated mares with no detected ovarian tumors is a consequence of an unusually high, apparently transient fluctuation in circulating testosterone at the time of mounting.  相似文献   

18.
Cyclic gilts from Control (C, randomly selected, n = 11) and Relax Select (RS, nine generations of selection for increased ovulation rate followed by seven generations of relaxed or random selection, n = 9) lines of the University of Nebraska Gene Pool population (derived from 14 different breeds) were utilized to characterize differences in gonadotropic and ovarian steroid hormones during preovulatory and postovulatory phases of the estrous cycle. Blood samples were collected during four periods (0500, 1100, 1700 and 2300) daily beginning 2 d prior to anticipated estrus (d -2, d 18 of a 20-d estrous cycle), and continuing through d 4 postestrus (d 0 = 1st of standing estrus). Sampling within a period consisted of five blood samples at 15-min intervals. All plasma samples were analyzed for concentrations of follicle stimulating hormone (FSH) and luteinizing hormone (LH). Neither mean LH nor peak concentration of LH during the preovulatory surge differed between genetic lines (P greater than .10). Concentrations of FSH increased faster (line X period, P less than .05) and tended (P less than .1) to peak at a higher concentration in RS (.88 ng/ml) than in C (.54 ng/ml) gilts (P less than .05) during the 12 h preceding the FSH and LH preovulatory peaks. The second FSH surge began approximately 24 h after the preovulatory FSH peak. Peak FSH concentrations were observed at 42 h in both lines (1.46 vs 1.74 ng/ml for C and RS gilts, respectively). The higher FSH concentration in RS gilts established during the preovulatory surge was maintained through the second FSH surge (P less than .01). No line differences were detected in plasma concentrations of estradiol-17 beta and progesterone.  相似文献   

19.
Granulosa cells from pooled bovine follicles were cultured under chemically-defined (serum-free) conditions to study the effects of exogenous steroids and FSH on production of immunoactive (ia) inhibin, oestradiol and progesterone. Levels of ia-inhibin in media samples and cell lysates were measured by radioimmunoassay (RIA) using an antiserum raised against a synthetic fragment of human inhibin -subunit [hI(1–32)].

Cells secreted measurable amounts of ia-inhibin, oestradiol and progesterone for at least 7 d of culture, although intracellular levels of inhibin were very low, indicating that newly-synthesized ia-inhibin is rapidly released from the cells. Treatment with androstenedione (0.2μmol/l) or testosterone (0.2μmol/l) increased ia-inhibin secretion markedly; levels on Day 5 of culture were approximately 6-fold (P<0.005) higher than control values. In contrast, treatment with the non-aromatizable androgen dihydrotestosterone (DHT; 0.2μmol/l) resulted in only a one- to two-fold increase (P<0.05) over control values (Day 5). Addition of exogenous oestradiol (8nmol/l) markedly increased ia-inhibin secretion (8–9 fold on Day 5; P<0.05) compared with basal levels, whereas progesterone had no effect. Secretion of oestradiol, undetectable in the absence of exogenous androgens, rose daily in the presence of either androstenedione or testosterone, levels rising approximately 6-fold and 9-fold respectively over a 4-d treatment period. Progesterone secretion increased 2-fold over the culture period and was unaffected by any steroid treatment.

Treatment with ovine FSH (10ng/ml) alone stimulated secretion of progesterone over basal levels (3-fold higher on Day 6; P<0.005), but did not affect output of either ia-inhibin or oestradiol. However, exposure to FSH in the presence of androstenedione not only promoted a further 4-fold increase in progesterone output but also led to a dose-dependent suppression of both ia-inhibin (90% lower on Day 6; P<0.001) and oestradiol (80% lower on Day 6; P<0.001) secretion compared to cells treated with androstenedione alone.

These observations indicate that the secretion of ia-inhibin by bovine granulosa cells in culture is positively regulated by oestradiol, implying an autocrine/paracrine role for this hormone in control of ovarian inhibin production. The ability of aromatizable androgens to stimulate secretion of inhibin, coupled with the inability of the non-aromatizable androgen DHT to elicit such an effect, suggests that inhibin output is largely unaffected by androgens prior to their conversion to oestradiol. The absence of any change in output of ia-inhibin or oestradiol following treatment with exogenous progesterone argues against a local role for this steroid hormone in regulation of inhibin or oestradiol production in the bovine follicle. Finally, the observation that co-treatment with FSH and andostenedione not only stimulated progesterone output but also suppressed secretion of ia-inhibin and oestradiol, indicates a synergistic positive effect of FSH and androgens on cellular luteinization.  相似文献   


20.
A heterologous radioimmunoassay developed to measure inhibin in rat plasma was validated and used to characterize changes in peripheral concentrations of immunoreactive inhibin (ir-inhibin) in relation to follicle stimulating hormone (FSH) concentrations during the estrous cycle of mares. The primary antiserum used in the assay was developed against a synthetic porcine inhibin -subunit [(1-26)-Gly-Tyr] fragment. The same synthetic peptide was used for preparation of standards and tracer. Slopes of the dose-response curves for pooled estrus and diestrus mare plasma and equine follicular fluid were similar to the slopes for the porcine inhibin -subunit standard curve and porcine follicular fluid dose-response curve. Twelve mares were bled once daily beginning when diameter of the largest follicle reached ≤25 mm and continuing until 3 days after the end of an interovulatory interval (ovulation=Day 0). Each of the 12 interovulatory intervals were normalized to the mean length of the interovulatory interval (22.2 days; range, 19 to 26). There was an effect of day for concentrations of ir-inhibin (P<0.001) and FSH (P<0.006). Significant mean changes were as follows: 1) ir-inhibin decreased between Days 0 and 1, whereas FSH increased between Days 0 and 5; and 2) ir-inhibin increased between Days 7 and 12, whereas FSH decreased between Days 11 and 14. Mean concentrations of ir-inhibin and FSH were negatively correlated (r=-0.548; P<0.002). In conclusion, mean peripheral concentrations of ir-inhibin and FSH were inversely related during the estrous cycle of mares.  相似文献   

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