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1.
Growth hormone (GH) has diverse actions in many tissues, including the follicle. This paper summarizes three experiments that examined the effects of GH and insulin-like growth factor (IGF)-I on the ovary. Ewes given oGH and pregnant mane serum gonadotrophin were compared with control and pregnant mane serum gonadotrophin-treated ewes. Ewes, with synchronized cycles, were given varying doses of pregnant mane serum gonadotrophin and/or oGH to determine if oGH is able to augment ovulation rate (Experiment 1). Experiments 2 and 3 used the ovarian autotransplant model. Ewes were infused via the ovarian artery with oGH (Experiment 2) or insulin-like growth factor I (IGF-I) (Experiment 3). Both were administered for 12 hr on Day 10. In Experiment 2, ewes were given intravenous gonadotropin releasing hormone (150 ng i.v.) at -2.5 and 10.5 hr relative to infusion. Ovarian and jugular venous blood was collected every 15 min from -30 to 150 min relative to gonadotropin releasing hormone. In Experiment 3, luteolysis was induced at the end of infusion. Ovarian and jugular venous blood was collected every 3 hr from before and until 84 hr after the infusion. Estradiol and androstenedione were assayed in ovarian venous plasma and GH in jugular venous plasma. In Experiment 1, treatment with oGH increased the jugular venous concentration of GH. However, in Experiment 2 treatment with oGH via the ovarian artery did not increase jugular venous GH but did increase ovarian venous GH. Treatment with oGH had no effect on ovulation rate (Experiment 1) or the secretion of androstenedione and estradiol (Experiment 2). Infusion of IGF-I (Experiment 3) increased the secretion of estradiol during the follicular phase. These data show that short-term treatment of sheep with GH had no in vivo effects on the follicle and that IGF-I was a potent stimulator of follicular steroidogenesis in vivo.  相似文献   

2.
Coat colour contributes to physiological adaptation in mammals and mediates response to thermal stress. Twenty-four adult West African Dwarf sheep of both sexes and with different coat colour types were used in this study. We measured rectal temperature (RT), respiratory rate (RR) and pulse rate (PR) before sunrise and sunset during the late dry season (January–March) and early rainy season (April–June) as well as packed cell volume (PCV), red blood cell (RBC) count, white blood cell (WBC) count, plasma sodium (Na+) and potassium (K+). Animals with black coat colour had the highest (P?<?0.05) mean values of 38.92?±?0.03 °C, 65.09?±?1.06 breaths/min, 81.35?±?0.78 beats/min, 1.70?±?0.01 for RT, RR, PR and heat stress index (HSI), respectively, followed by brown mouflon and brown with extensive white, while the Badger Face coloured sheep had the least mean values. There were significant (P?<?0.05) differences between male and female sheep for RT, RR, PR and HSI. Season had a significant (P?<?0.05) effect on RT, RR, PR and HSI. Coat colour and sex also significantly (P?<?0.01) affected RBC, WBC, Na+ and K+. Seasonal variation (P?<?0.05) in all the blood parameters was observed, with the exception of PCV. Interaction effect of coat colour and sex was significant (P?<?0.05) on RT and HSI. Correlation coefficients among the measured traits ranged from positive to negative values. These results indicate that selection of white-coloured sheep to attenuate heat stress is desirable in the hot humid tropics.  相似文献   

3.
The aim of the study was to determine the effects of various doses of injected Se on the physiological responses of sheep to heat load. Fifteen 9-mo-old Australian Merino wethers (mean BW = 27.2 ± 2.1 kg) were randomly assigned to 1 of 3 treatments: 0 (control), 0.5, and 5 mg of Se, which was administered as a subcutaneous sodium selenate injection (5 mg/mL Se) on d 1, 8, and 15 of exposure to heat stress. The animals were housed individually in an environmental chamber and exposed to high temperature from 0700 to 1800 h (maximum = 38°C; minimum = 24°C) and to thermoneutral temperature from 1800 to 0700 h (maximum = 24°C; minimum = 20°C) for 21 d. Rectal temperature (RT) and respiration rate (RR) were measured daily at 0800, 1200, and 1600 h. Feed intake was measured daily, and sheep were weighed on d 1, 8, 15, and 21. Blood samples were collected on d 1 and 21. The 5 mg Se treatment decreased RT by 0.3°C (P = 0.02) and BW loss by 4.5% (P < 0.05) and increased eosinophil count (P < 0.05). There were no differences (P > 0.05) between treatments in RR and DMI, serum concentrations of glucose, total protein, cholesterol, and NEFA or in blood hematology variabl6es. The findings of this study have important implications for the sheep industry. Further studies are warranted to elucidate the dynamics of Se on productivity and health during hot conditions.  相似文献   

4.
1. The effects of tap (TW) or carbonated (CW) water on arterial pH, partial pressure of carbon dioxide (PCO2) and plasma lactate were determined in heat-stressed broilers. Water treatments were infused directly into the crop at a rate of 0.4 ml/min kg BW. 2. Heat stress increased body temperature (Tb) and respiration rate (RR) but both were higher in birds given CW after 4 and 5 h than in TW-infused controls. However, PCO2 was lower and arterial pH and plasma lactate were higher in TW-infused birds after 4 and 5 h of heat stress than in CW-infused birds. Hematocrit was also higher in CW-treated birds after 4 and 5 h of heat stress than in TW controls. 3. The results indicate that CW is capable of attenuating changes in blood pH and PCO2 in heat-stressed domestic fowl. The lower pH in CW birds after 4 and 5 h of heat stress may have suppressed plasma lactate concentrations in these birds.  相似文献   

5.
Experiments were conducted to examine the effects of exogenous GnRH and LH on serum concentrations of progesterone (P4) in the ewe. Ewes in Exp. 1 and 2 were laparotomized on d 2 of an estrous cycle and ewes with corpora lutea (CL) in both ovaries were unilaterally ovariectomized. Ewes with CL in one ovary only were not ovariectomized. While they were anesthetized, ewes (n = 5) were injected with 25 micrograms GnRH (Exp. 1) or 50 ng GnRH (Exp. 2) into the artery supplying the ovary bearing the CL. Control ewes (n = 5 in each experiment) were injected similarly with saline. In Exp. 3, six ewes were injected i.v. (jugular) on d 2 with 100 micrograms oLH (t = 0) and 50 micrograms oLH at 15, 30 and 45 min; six control ewes were injected similarly with saline. Jugular blood was collected from all ewes at frequent intervals after treatment for LH analysis and on alternate days of the cycle through d 10 or 11 for P4 analysis. Treatment with 25 micrograms GnRH increased serum concentrations of LH at 15, 30, 45 and 60 min postinjection (P less than .001) and reduced serum concentrations of P4 on d 7 through 11 (treatment x day interaction; P less than .05). Injection with 50 ng GnRH caused a slight increase in serum concentrations of LH at 15 min but had no effect on serum concentrations of P4.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

6.
Effects of heat stress on multiparous lactating Holstein cows were evaluated in a continuous design in natural environments (a shade management system vs no shade, n = 6/treatment, early- to mid-lactation cows) and in a single-reversal design in climatic chambers (thermoneutral vs thermal stress, n = 4/treatment, mid- to late-lactation cows). Objectives were to compare effects of nycterohemeral heat stress vs nonheat stress environments on acid-base status, mineral concentrations and rates of ruminal liquid dilution and solid phase digesta turnover. In the shade vs no shade experiment, the complete mixed diet consisted of 38% corn silage and 62% corn-based concentrate mix. In the chamber experiment, the diet consisted of 40% alfalfa haylage and 60% corn-based concentrate mix. In both experiments, respiration rates, rectal temperatures, blood and urine were sampled hourly for 26 h. Measurements of rectal temperature, respiration rate and blood gas composition indicated that chamber heat stress simulated natural heat stress. In both experiments, cows exhibited signs of respiratory alkalosis only during hours of heat stress. Ruminal turnover rates of liquid were measured with chromium-ethylenediaminetetraacetate and solid turnover rates with ytterbium-marked fecal fiber, both dosed through the ruminal cannula. Turnover rates of liquid and solid digesta and total volatile fatty acids were lower in the heat stress vs the thermoneutral environment. The results illustrate the necessity of frequent sampling to characterize nycterohemeral patterns of physiological measurements during heat stress.  相似文献   

7.
Ten non‐lactating multiparous Pelibuey breed ewes were housed in a corral to evaluate the effects of summer thermal stress on physiologic variables, estrous behavior, ovulation and corpus luteum functionality under natural conditions of an arid region. In summer and autumn, daily estrous detection with a ram fitted with an apron and blood sample collections were performed during two natural estrous cycles. An environment of heat stress was detected in summer and thermoneutral in autumn. Rectal temperature and respiratory frequency were greater (P < 0.01) in summer than in autumn during the morning and afternoon. Season did not affect (P > 0.05) live weight, body condition, length of estrous cycle or percentage of ewes in estrous and ovulating. Compared with autumn, serum progesterone concentrations in summer decreased (P < 0.05) between days 8 and 14 of the estrous cycle. It is concluded that under outdoor conditions of arid regions, while estrous and ovulatory activities of Pelibuey ewes were not affected by summer thermal stress, the corpus luteum functionality was decreased.  相似文献   

8.
The aim of the present study was to evaluate the effect of shearing on physiological and oxidative stress parameters in ewes. Twenty Comisana ewes were used and divided into two groups. Ten ewes were left unshorn as a control group (Group A) and 10 ewes were shorn (Group B). All measurements were taken before and after shearing, and repeated 8 h after shearing and 1, 2, 3, 4, 5, 10 and 15 days after shearing. Reactive oxygen species (dROMs), antioxidant barrier (oxy‐adsorbent), thiol antioxidant barrier (SHp) and packed cell volume (PCV) were assessed in blood samples collected by means of jugular venipuncture. Rectal temperature (RT), respiratory rate (RR) and heart rate (HR) were also measured. Two‐way repeated measures analysis of variance (ANOVA), followed by Bonferroni's test, was used for the assessment of significant effects due to shearing and time. The statistical analysis showed significant increases (P < 0.01) of dROMs, oxy‐adsorbent, SHp, and a significant decrease (P < 0.01) of RT and RR associated with time and shearing. Our results indicate that shearing causes a change in the ewe's homeostatic balance that leads to oxidative stress.  相似文献   

9.
1. The effects of ammonium chloride (NH4Cl) on the bicarbonate buffer system and plasma lactate in heat-stressed broilers were investigated. 2. The infusion of a 10 g/l solution of NH4Cl into the crop during a 90 min thermoneutral period produced a metabolic acidosis resulting from a reduction in blood bicarbonate concentration. Blood bicarbonate continued to decrease in NH4Cl-treated birds and reached values which were 30% of controls by the end of a 90 min heat stress period. 3. By the end of heat stress, plasma lactate concentrations were lower in NH4Cl-infused birds than in controls.  相似文献   

10.
Pregnant ewes were chronically exposed to thermoneutral (TN; 20 degrees C, 30% relative humidity) or hot (H; 40 degrees C 9 h/d, 30 degrees C 15 h/d, 40% relative humidity) environments between d 64 and 136 to 141 of pregnancy. They were sampled for blood at 14-d intervals during this period for measurement of plasma metabolites and hormones, then slaughtered and dissected to measure conceptus weights, dimensions and fetal organ weights. Rectal temperatures of H ewes were elevated .3 to 1.0 C degrees above those of TN ewes throughout the experiment. Voluntary feed intakes were not altered by heat exposure except after 120 d of pregnancy, when feed intake was about 25% lower (P less than .10) by H than by TN ewes. Blood 3-hydroxybutyrate concentrations were not affected by heat, but plasma glucose concentrations were greater in H than in TN animals after 120 d (P less than .05). Placental weight, reduced by 54% (P less than .001) by heat exposure of ewes, was correlated positively with fetal weight and correlated negatively with fetal/placental weight ratio, fetal brain/liver weight ratio and fetal relative heart weight. Late in pregnancy, plasma concentrations of progesterone, cortisol and placental lactogen were reduced (P less than .01) in H ewes, whereas triiodothyronine levels were markedly lower (P less than .03) at all stages of pregnancy. Plasma concentrations of prolactin were elevated dramatically (P less than .01) and a modest increase (P less than .03) in somatotropin levels was recorded in H ewes. These results are consistent with our hypothesis that heat-induced fetal growth retardation is secondary to a primary reduction in placental growth; this could be mediated partly by reduced peripheral activity of thyroid hormones. Heat-induced reductions in secretion of progesterone and ovine placental lactogen more likely were a consequence than a cause of placental stunting.  相似文献   

11.
AIM: To determine the plasma cortisol response to laparoscopy in ewes and investigate means of reducing it. METHODS: Ewes without lambs at foot (n=40) were subjected to one of three control or one laparoscopy treatments (n=10 ewes/treatment), being: no restraint or drugs; acepromazine maleate (ACP) control and no restraint; ACP and restraint in a cradle for 5 min; and laparoscopy following ACP. Additional ewes with lambs at foot (n=30) were subjected to: laparoscopy following ACP; laparoscopy following ACP and ketoprofen; and laparoscopy following detomidine. Drugs were injected 20 min before treatment, after a first blood sample had been taken. Blood samples were taken by jugular venepuncture from the ewes 20 min before treatment and at 20, 40, 60, 90, 120, 150 and 180 min after treatment, while all ewes were held in a pen. Plasma was harvested and assayed for its concentration of cortisol. RESULTS: Plasma cortisol concentrations (PCC) remained constant in ewes in the control restraint group for 80 min. In ewes given ACP, PCC increased for the first 20 min after treatment but then returned to pre-treatment concentrations. PCC of ewes given ACP and restrained in a cradle were elevated above pre-treatment concentrations for 90 min. PCC in ewes subjected to laparoscopy following sedation with ACP increased to a peak at 40 min and returned to pre-treatment concentrations after 60 (with lambs) or 120 (without lambs) min. When ACP and ketoprofen were given before laparoscopy, PCC peaked at 20 min and returned to pre-treatment concentrations by 40 min. PCC of ewes given detomidine before laparoscopy remained at pre-treatment concentrations throughout. PCC of ewes subjected to laparoscopy with ACP sedation only were greater than those of control restraint, ACP control, and ewes subjected to laparoscopy after being given ketoprofen or detomidine between 20 and 60 min after treatment. PCC of ewes subjected to laparoscopy were greater than those of control ewes placed in a cradle at 20 and 40 min. PCC of ewes given ketoprofen were lower than those of ewes subject to laparoscopy following ACP. CONCLUSIONS: Laparoscopy, even after sedation with ACP, caused some distress in ewes, as evidenced by increased plasma cortisol levels. Plasma cortisol response was alleviated by the administration of ketoprofen and eliminated by detomidine, probably because of both analgesic and sedative effects of the latter drug.  相似文献   

12.
The objective of the study was to determine whether the local permeability of luteinizing hormone-releasing hormone (LHRH) from the venous blood of the perihypophyseal cavernous sinus into the arterial blood of the carotid rete, supplying the brain and hypophysis in gilts, depends on the day of the estrous cycle, as well as to determine whether this transfer exists when LH concentration in the blood is reduced (the experimental short-loop negative feedback for LH secretion after estradiol injection in ovariectomized gilts). Experiments were conducted on isolated gilt heads with necks, on chosen days of the estrous cycle (n = 40), and on previously ovariectomized gilts treated with estradiol benzoate (EB) (n = 5) or corn oil (n = 3). After exsanguination, the gilt heads with necks were disarticulated and about 30–45 min later were supplied with autologous, oxygenated, and heated blood at a stable blood flow and pressure through the left carotid artery for 30 min. 125I-LHRH was infused into both cavernous sinuses through the cannulated angularis oculi veins for 5 min. After 125I-LHRH infusion, radiolabeled LHRH was found (P < 0.001) in arterial blood taken from the carotid rete through the open right carotid artery in all animals used in the experiment: on Days 1–2 (six gilts), on Days 12–14 (seven gilts) of the estrous cycle, and in five ovariectomized gilts during negative feedback for LH surge (40 hr after EB). No significant radioactivity of 125I-LHRH was found in the arterial blood on Days 3–5 (n = 6), 9–11 (n = 4), and 15–21 (n = 17) of the estrous cycle. A very low level of radioactivity was found in the ovariectomized control group after the injection of corn oil (n = 3). These results provide evidence for the permeability of LHRH from the venous to the arterial blood and its retrograde transport with the arterial blood to the hypophysis and brain, after the ovulation period (Days 1–2) and on Days 12–14 of the estrous cycle. This suggests that a close relationship exists between the day of the estrous cycle and LHRH permeability from the venous to the arterial blood in the perihypophyseal cavernous sinus—the carotid rete complex in gilts—and that this mechanism may be included in a short-loop feedback for LHRH secretion.  相似文献   

13.
Four nonlactating, nonpregnant, mature ewes equipped with multiple venous and arterial catheters were used to evaluate the influence of propionate as a satiety signal in ruminants. Our experiment was a 4 x 4 Latin square with portal infusion (physiological saline [Sa] or sodium propionate [Pr]) and DE intake (Lo, 63% of maintenance requirement, or Hi, 200% of maintenance requirement) as factors. One 240-min infusion of Pr (1 mmol/min) or Sa into the portal vein began at approximately 0800 on d 8 of each 8-d period. Feed intake was measured and hepatic blood was sampled every 30 min during infusion. Intake of DM and digestible energy (DEI) during infusion were not affected by infusion or diet and were most rapid at 30 min postfeeding. Average 30-min DMI and DEI were 539 g and 1,484 kcal, respectively, at 240 min. Cumulative DMI and DEI were unaffected by infusion but tended to be greater with Lo. After 30 min, animals tended to consume Lo at a greater rate than Hi, suggesting that satiety was delayed. Insulin concentration was increased (P less than .02) when animals consumed Hi (36.1 mU/liter) vs Lo (16.8 mU/liter) and was elevated (P less than .01) at 30 and 60 min postfeeding when animals were infused with Pr. Plasma acetate tended to be reduced with Pr infusion. Plasma Pr tended to increase with Pr infusion, especially when sheep were fed Lo. Satiety, DMI, and DEI were not affected by Pr infusion in this study.  相似文献   

14.
A study was conducted to assess the effect of multiple stresses (thermal, nutritional, and walking stress) on the adaptive capability of Malpura ewes in terms of changes in physiological mechanisms and blood biochemical changes. The study was conducted for a period of 35 days covering two estrous cycles during summer season (April–May). The ewes were randomly allocated into two groups of 12 animals each, viz., GI (n?=?12; control) and GII (n?=?12; multiple stresses). GI ewes were maintained in the shed while GII ewes were subjected to multiple stresses. GI ewes were maintained in shed while GII ewes were subjected to heat stress by exposing them to 32–44 °C (average 42 °C) and RH of 12–26 % for 6 h from 10:00 to 16:00 h in natural environment. GI ewes were provided with ad libitum feeding while GII ewes were provided with restricted feed (30 % of intake of GI ewes) to induce nutritional stress. Further, GII ewes were subjected to walking stress by forcing them to walk 14 km in two spans between 9:00 and 10:30 h and 15:00 and 16:30 h. Blood collection was done at weekly intervals. Multiple stresses significantly (P?<?0.01) affected body weight, respiration rate, pulse rate, rectal temperature, sweating rate, tri-iodo-thyronine, thyroxine, cortisol, hemoglobin, packed cell volume, glucose, and total protein. The findings from this experiment provide useful information to understand the ideal nutrient requirement for these animals to adapt to such stresses in the semi-arid tropical environment without compromising production.  相似文献   

15.
Effect of xylazine in heifers under thermoneutral or heat stress conditions   总被引：1，自引：0，他引：1  
A study was performed to assess the effect of xylazine HCl (0.1 mg/kg of body weight, IV) in heifers maintained at thermoneutrality (18 C, 42% humidity) or under heat stress (33 C, 63% humidity) conditions. Xylazine caused 50 and 70% decreases in serum insulin concentrations in the thermoneutral and heat-stressed heifers, respectively. Xylazine-induced hypoinsulinemia was associated with hyperglycemia. In the thermoneutral group, serum glucose concentrations increased from a basal concentration of 75 mg/dl to 150 mg/dl after 15 minutes. In the heat stress group, the serum glucose concentration increased from 65 mg/dl to 105 mg/dl. Hyperglycemia peaked at 2 hours and remained high for 6 hours after xylazine administration. Heat-stressed heifers took a longer time (107 minutes) to stand than did heifers under thermoneutral conditions (41 minutes). The time to regain sensation to pain was significantly prolonged in heat-stressed heifers. Xylazine had no effect on body temperature and respiration rate in heifers under the thermoneutral condition, whereas it markedly induced hyperthermia and suppressed respiration rate in the heat-stressed heifers. Furthermore, the pulse rate was slightly decreased in thermoneutral heifers and was markedly decreased in the heat-stressed heifers.  相似文献   

16.
Catheters were implanted in 6 anaesthetized gilts (3 animals in the follicular phase, 3 in the luteal phase) into a carotid artery and into the utero-ovarian vein and uterine artery on both sides. The uterine lumina were closed by a suture. Further, a catheter was inserted into the vagina after which the animals were allowed to recover. Tritiated progesterone was infused into vagina the following day during a 2 min period and simultaneous blood samples collected from the 5 catheters every 10 min for 2 h after which the animals were sacrificed. Tissue samples were obtained from the genital organs.The results showed a rapid absorption of progesterone from the vaginal lumen and a marked redistribution to the genital organs. The increased level of radioactivity in the plasma samples collected from the uterine arteries compared to the simultaneous samples from the carotid artery in 2 of the 3 animals in the luteal phase indicates the existence of a local redistribution system.  相似文献   

17.
Ovariectomized ewes (n=22; 68.76+/-2.34 kg initial body weight; 2.9+/-0.1 initial body condition score) were individually fed one of three diets: (1) control (phytoestrogen-free; n=7), (2) flax containing diet (n=8), or (3) linseed meal (LSM) containing diet (n=7) to investigate the rate of progesterone (P4) clearance. On day 20 of feeding (day 0=initiation of treatment), a P4 releasing device (CIDR) was placed in the vagina and jugular blood samples were obtained prior to CIDR insertion and 15, 30, 60, and 120 min following CIDR insertion. Further, blood samples were obtained daily between days 21 and 24. On day 25, blood samples were retrieved prior to CIDR removal and 2, 5, 10, 15, 30, 60, 120, and 360 min following CIDR removal. There was no difference in initial or final body weight or body condition score and there were no time by diet interactions on P4 clearance. The fractional rate of P4 uptake measured prior to CIDR insertion through day 4 following insertion tended to be greater (P=0.07) in LSM fed ewes (508.75+/-71.37%/min) compared to flax (295.39+/-66.76%/min) and control fed (287.54+/-71.37%/min) ewes. Diet tended (P=0.10) to influence P4 clearance rate when measured from prior to CIDR removal through 120 min following CIDR removal with LSM fed ewes having a greater (1.26+/-0.2) fractional rate constant than flax (0.929+/-0.09) and control fed (0.922+/-0.09) ewes. Flax fed ewes also had more (P<0.01) omega-3 fatty acids and total fatty acids in plasma. Reports of increased pregnancy rates in dairy cows fed flax may relate to P4 metabolism.  相似文献   

18.
Hepatic monoxygenases metabolize steroids that in turn influence reproduction. Experiments were conducted to establish the effect of dose of phenobarbital and level of dietary protein on hepatic monoxygenase. In Exp. 1, ewes were given either 0, .5, 1, 2 or 3 g phenobarbital (PB) daily for 4 to 8 d. After 48 h after last dose of PB, cytochrome P-450 was higher (P less than .01) in all ewes given PB than in controls and was higher (P less than .01) in ewes given PB for 8 d than in ewes treated for 4 d. In Exp. 2, either 0 or 1 g of PB was given orally for 8 d. Liver samples were collected 1, 4, 7 or 10 d after last treatment. Both cytochrome P-450 (P less than .01) and nicotinamide adenine dinucleotide phosphate (NADPH) cytochrome c reductase (P less than .06) were higher in ewes receiving PB than in controls. Cytochrome P-450 was twice as high in treated ewes as in control ewes on the 8th d of treatment, but concentrations returned to control levels 10 d after last treatment. Microsomal protein and cytochrome b5 were not affected by PB (P greater than .10). Ewes in Exp. 3 receiving a diet containing 14.8% crude protein for 10 d had higher levels of cytochrome P-450 (P less than .01) than ewes fed 4.7% crude protein. Protein did not affect microsomal protein or NADPH cytochrome c reductase. These data suggest that a relationship among PB, dietary protein and monoxygenases exists and provide information that will lead to a better understanding of the relationship between diet and reproduction.  相似文献   

19.
Two experiments were conducted with ewes 9 to 11 days after estrus to determine whether the secretion of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) are controlled differentially. In experiment 1, gonadotropin-releasing hormone (GnRH) was injected (100 (μg/ewe) at time = 0 min into ewes in four treatment groups. The treatment groups (9 ewes/group) were: 1) periodic iv sodium pentobarbital (NaPen) vehicle from 0 min; 2) periodic iv NaPen from 0 min; 3) vehicle iv for 120 min then iv NaPen from 120 min; 4) vehicle iv for 150 min then iv NaPen from 150 min. A surgical plane of anesthesia was maintained from the initiation of NaPen injection until the experiment ended. Jugular blood was sampled at 30-min intervals from ?30 to + 210 min for LH and FSH assays, and profiles of hormone concentrations were compared by time-trend analyses. GnRH released LH (P<.001) and FSH (P<.001), but NaPen did not affect the profiles of hormone concentrations; this indicated that NaPen did not reduce the ability of the pituitary to secrete gonadotropins in response to GnRH. Experiment 2 was a 2x2 factorial with ovariectomy (time = 0 hr) and NaPen as the main effects. One group of ovariectomized (n = 6) and one group of sham ovariectomized (n = 6) ewes were anesthetized only during surgery, while a group of ovariectomized (n = 7) and a group of sham ovariectomized (n = 6) ewes were kept at a surgical plane of anesthesia until 10 hr after surgery. Patterns of LH and FSH were compared in jugular blood collected hourly from 0 hr until 10 hr after surgery and in samples collected at 24 hr intervals from -24 to +72 hr of surgery. After ovariectomy, LH increased (P<.001) hourly and daily, but anesthesia suppressed (hourly, <.001 and daily, P<.005) these increases, which resulted in an interaction (hourly, P<.001 and daily, P<.01) of ovariectomy and anesthesia. FSH after ovariectomy increased hourly and daily (hourly, P<.02 and daily, P<.001), but the effect of anesthesia and interaction of ovariectomy and anesthesia were not significant. Because NaPen did not alter secretion of LH or FSH after exogenous GnRH in experiment 1 while it blocked the postovariectomy increase in LH but not FSH in experiment 2, we concluded that the postovariectomy increase in LH resulted from increased hypothalamic secretion of GnRH. The mechanisms responsible for the postovariectomy increase in FSH secretion are not identical to those for LH. The mechanisms that control the postovariectomy secretion of FSH might involve factors that are not suppressible by NaPen or, alternatively, the differences in LH and FSH release after ovariectomy might reflect the removal of ovarian factors that suppress FSH but not LH secretion in intact ewes.  相似文献   

20.
Three experiments were conducted to examine the relationship between systemic concentrations of luteinizing hormone (LH) and estradiol-17 beta (E2) after withdrawal of progesterone in cycling ewes. In Exp. 1, ewes were assigned randomly to one of three treatments: laparotomy (C), removal of the luteal ovary (ULO), or ULO plus anesthesia with sodium pentobarbital for 6 h beginning 4 h after surgery. Anesthesia was used in an attempt to block the expected increase in tonic secretion of LH. Patterns of LH and E2 in these three groups did not differ during the 24-h experimental period. In Exp. 2, a longer period of anesthesia was utilized. Forty-eight ewes were assigned at random to one of four treatments: C, ULO, lutectomy or an intrafollicular injection of prostaglandin F2 alpha (PGF2 alpha). One-half of the ewes in each group were anesthetized with sodium pentobarbital from initiation of treatment (0 h) until 10 h after surgery. Sodium pentobarbital did not suppress the increases in LH and E2 after progesterone withdrawal. The regression of concentrations of E2 on concentration of LH was not significant. In Exp. 3, ewes were infused with either saline or dopamine after receiving an im injection of PGF2 alpha. Tonic secretion of LH increased after 4 h in ewes infused with saline, but not in ewes infused with dopamine. Despite the suppression of LH, concentrations of E2 increased in dopamine-treated ewes as in control ewes. Therefore, the initial increase in E2 after a decline of progesterone in cycling ewes is independent of increases in LH.  相似文献   

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