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1.
Changes in serum concentrations of glucose and insulin after iv injection of a low (20 mU/kg) and high (200 mU/kg) dose of bovine insulin were used to quantify insulin resistance and calculate kinetic variables of injected insulin, respectively, in four obese and four lean heifers. Serum samples from jugular venous blood were collected 60, 45, 30, 15 and 1 min before and 2.5, 5, 10, 20, 30, 40, 60, 80, 100, 120, 150, 180, 210 and 240 min after each treatment. Mean (+/- SE) pretreatment concentration of insulin (microU/ml) was higher (P less than .01) in obese (50 +/- 6.6) than lean (20 +/- 1.8) heifers, even though glucose concentrations were similar in both groups (71 +/- 2.9 mg/100 ml). Concentrations of insulin after each treatment were similar in both groups and returned to pretreatment values by 60 and 120 min after injection of the low and high doses, respectively. Glucose concentrations during the first 40 min after treatment with the low dose were lower (P less than .05) in lean than obese heifers, but were similar in both groups during the first 40 to 60 min after the high dose of insulin. The high insulin dose decreased (P less than .05) glucose concentrations below those of the low dose in each group, but the difference was greater (P less than .01) in obese than lean heifers. These results indicated that obese heifers were insensitive to the glucoregulatory effects of exogenous insulin, although the maximum responses to insulin were similar.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

2.
Effects of degree of obesity on basal concentrations of insulin, glucose, thyroxine (T4), triiodothyronine (T3), estradiol-17 beta (E) and progesterone (P) were measured in serum from 50 estrous and 73 diestrous Holstein heifers and the insulin response to glucose infusion was assessed in diestrous obese (n = 7) and lean (n = 7) heifers. Basal concentrations of glucose, T4, T3, E and P were not correlated with degree of obesity, although concentrations of glucose, T4 and T3 were higher (P less than .05) at estrus than diestrus. Basal concentrations of insulin at estrus and diestrus were positively correlated (r = .6; P less than .001) with degree of obesity but this relationship was different (P less than .001) between estrus and diestrus. Furthermore, there was interaction (P less than .001) between body condition and stage of the estrous cycle only for basal concentrations (mean +/- SE) of insulin, with the difference in insulin levels (microU/ml) between 12 obese and 12 lean heifers at diestrus (11.7 +/- 1.3 vs 6.7 +/- .6; P less than .05) increasing during estrus (21.9 +/- 2.4 vs 10.8 +/- 1.3; P less than .001). Insulin response to glucose infusion was greater in obese than in lean heifers, whether determined as actual concentration (P less than .01) or as insulin response areas (P less than .05) above base-line concentrations. Obese heifers were less responsive to insulin since hyperinsulinemia and euglycemia coexisted, and because glucose fractional removal rates were similar in both groups after glucose infusion in spite of greater concentrations of insulin in obese heifers. Thus, obesity in heifers was associated with insulin resistance, basal hyperinsulinemia and greater glucose-induced secretion of insulin.  相似文献   

3.
OBJECTIVE: To determine whether dietary fatty acids affect indicators of insulin sensitivity, plasma insulin and lipid concentrations, and lipid accumulation in muscle cells in lean and obese cats. ANIMALS: 28 neutered adult cats. PROCEDURE: IV glucose tolerance tests and magnetic resonance imaging were performed before (lean phase) and after 21 weeks of ad libitum intake of either a diet high in omega-3 polyunsaturated fatty acids (3-PUFAs; n = 14) or high in saturated fatty acids (SFAs; 14). RESULTS: Compared with the lean phase, ad libitum food intake resulted in increased weight, body mass index, girth, and percentage fat in both groups. Baseline plasma glucose or insulin concentrations and glucose area under the curve (AUC) were unaffected by diet. Insulin AUC values for obese and lean cats fed 3-PUFAs did not differ, but values were higher in obese cats fed SFAs, compared with values for lean cats fed SFAs and obese cats fed 3-PUFAs. Nineteen cats that became glucose intolerant when obese had altered insulin secretion and decreased glucose clearance when lean. Plasma cholesterol, triglyceride, and non-esterified fatty acid concentrations were unaffected by diet. Ad libitum intake of either diet resulted in an increase in both intra- and extramyocellular lipid. Obese cats fed SFAs had higher glycosylated hemoglobin concentration than obese cats fed 3-PUFAs. CONCLUSION AND CLINICAL RELEVANCE: In obese cats, a diet high in 3-PUFAs appeared to improve long-term glucose control and decrease plasma insulin concentration. Obesity resulted in intra- and extramyocellular lipid accumulations (regardless of diet) that likely modulate insulin sensitivity.  相似文献   

4.
Glucose tolerance and insulin response in normal-weight and obese cats   总被引：2，自引：0，他引：2  
Glucose tolerance and insulin response were evaluated in 9 normal-weight and 6 obese cats after IV administration of 0.5 g of glucose/kg of body weight. Blood samples for glucose and insulin determinations were collected immediately prior to and 2.5, 5, 7.5, 10, 15, 30, 45, 60, 90, and 120 minutes after glucose infusion. Baseline glucose concentrations were not significantly different between normal-weight and obese cats; however, mean +/- SEM glucose tolerance was significantly impaired in obese vs normal-weight cats after glucose infusion (half time for glucose disappearance in serum--77 +/- 7 vs 51 +/- 4 minutes, P less than 0.01; glucose disappearance coefficient--0.95 +/- 0.10 vs 1.44 +/- 0.10%/min, P less than 0.01; insulinogenic index--0.20 +/- 0.02 vs 0.12 +/- 0.01, P less than 0.005, respectively). Baseline serum insulin concentrations were not significantly different between obese and normal-weight cats. Insulin peak response after glucose infusion was significantly (P less than 0.005) greater in obese than in normal-weight cats. Insulin secretion during the first 60 minutes (P less than 0.02), second 60 minutes (P less than 0.001), and total 120 minutes (P less than 0.0003) after glucose infusion was also significantly greater in obese than in normal-weight cats. Most insulin was secreted during the first hour after glucose infusion in normal-weight cats and during the second hour in obese cats. The impaired glucose tolerance and altered insulin response to glucose infusion in the obese cats was believed to be attributable to deleterious effects of obesity on insulin action and beta-cell responsiveness to stimuli (ie, glucose).  相似文献   

5.
Dogs do not appear to progress from obesity-induced insulin resistance to type 2 diabetes mellitus. Both postprandial hyperglycemia and postprandial hypertriglyceridemia have been proposed to cause or maintain beta cell failure and progression to type 2 diabetes mellitus in other species. Postprandial glucose, triglyceride, and insulin concentrations have not been compared in lean and obese dogs. We measured serum glucose, triglyceride, and insulin concentrations in nine naturally occurring obese and nine age- and gender-matched lean dogs. After a 24-h fast, dogs were fed half their calculated daily energy requirement of a standardized diet that provided 37% and 40% of metabolizable energy as carbohydrate and fat, respectively. Fasting and postprandial glucose and triglyceride concentrations were greater in the obese dogs (P < 0.001), although the mean insulin concentration for this group was five times greater than that of the lean group (P < 0.001). Most of the 0.6 mM (11 mg/dL) difference in mean postprandial glucose concentrations between lean and obese dogs was attributable to a subset of persistently hyperglycemic obese dogs with mean postprandial glucose concentrations 1.0 mM (18 mg/dL) greater than that in lean dogs. Persistently hyperglycemic obese dogs had lower triglyceride (P = 0.02 to 0.04) and insulin (P < 0.02) concentrations than other obese dogs. None of the dogs developed clinical signs of diabetes mellitus during follow-up for a median of 2.6 yr. We conclude that pancreatic beta cells in dogs are either not sensitive to toxicity because of mild hyperglycemia or lack another component of the pathophysiology of beta cell failure in type 2 diabetes mellitus.  相似文献   

6.
OBJECTIVE: To examine whether obese cats, compared with lean cats, have alterations in lipoprotein metabolism that might lead to a decrease in glucose metabolism and insulin secretion. ANIMALS: 10 lean and 10 obese adults cats (5 neutered males and 5 neutered females each). PROCEDURE: Intravenous glucose tolerance tests with measurements of serum glucose, insulin, and nonesterified fatty acid (NEFA) concentrations were performed. Lipoprotein fractions were examined in serum by isopycnic density gradient ultracentrifugation. RESULTS: Obese cats had insulin resistance. Plasma triglyceride and cholesterol concentrations were significantly increased in obese cats, compared with lean cats. Very low density lipoprotein (VLDL) concentrations were increased in obese cats, compared with lean cats; however, the composition of various fractions remained unchanged between obese and lean cats, indicating greater synthesis and catabolism of VLDL in obese cats. Serum high density lipoprotein (HDL) cholesterol concentrations were increased in obese cats, compared with lean cats. Serum NEFA concentrations were only significantly different between obese and lean cats when separated by sex; obese male cats had higher baseline serum NEFA concentrations and greater NEFA suppression in response to insulin, compared with lean male cats. CONCLUSIONS AND CLINICAL RELEVANCE: Lipid metabolism changes in obese cats, compared with lean cats. The increase in VLDL turnover in obese cats might contribute to insulin resistance of glucose metabolism, whereas the increase in serum HDL cholesterol concentration might reflect a protective effect against atherosclerosis in obese cats.  相似文献   

7.
Three experiments were conducted to evaluate plasma concentrations of glucose, insulin, IGF-I, and progesterone (P4) in pubertal beef heifers receiving exogenous glucose, insulin, or sometribove zinc. All heifers used had no luteal P4 synthesis but received a controlled internal drug-releasing device containing 1.38 g of P4 to estimate treatment effects on hepatic P4 degradation. In Exp. 1, 8 pubertal, nulliparous Angus × Hereford heifers (initial BW = 442 ± 14 kg; initial age = 656 ± 7 d) were randomly assigned to receive, in a crossover design containing 2 periods of 10 h, intravenous (i.v.) infusions (10 mL) of insulin (1 μg/kg of BW; INS) or saline (0.9%; SAL). Treatments were administered via jugular venipuncture in 7 applications (0.15 μg insulin/kg BW per application) 45 min apart (from 0 to 270 min). Blood samples were collected immediately before each infusion as well as at -120, -60, 330, 390, and 450 min relative to the first infusion. Heifers receiving INS had greater (P < 0.01) plasma insulin, reduced (P ≤ 0.04) plasma glucose and IGF-I, and similar (P = 0.62) plasma P4 concentrations compared with SAL heifers. In Exp. 2, the same heifers were assigned to receive, in a similar experimental design as Exp. 1, i.v. infusions (10 mL) of 1) insulin (1 μg/kg BW) and glucose (0.5 g/kg BW; INS+G) or 2) SAL. Heifers receiving INS+G had greater (P ≤ 0.02) plasma insulin, glucose, and P4 but reduced (P = 0.01) plasma IGF-I concentrations compared with SAL heifers. In Exp. 3, the same heifers were assigned to receive, in a crossover design containing 2 periods of 14 d, subcutaneous (s.c.) injections of 1) 250 mg of sometribove zinc (BST) or 2) SAL. Blood samples were collected 3 h apart (0900, 1200, 1500, and 1800 h) from heifers on d 6, 8, and 10 relative to treatment administration (d 1). Heifers receiving BST had greater (P < 0.01) plasma glucose and IGF-I and similar (P ≥ 0.67) plasma insulin and P4 concentrations compared with SAL heifers. Results from this series of experiments suggested that concurrent increases in glucose and insulin are required to reduce hepatic catabolism and increase plasma concentrations of P4 in bovine females.  相似文献   

8.
The response to oral glucose was examined in 10 obese and 9 lean age-matched, neutered cats. In all cats, oral administration of 2 g/kg glucose was followed by a prompt increase in glucose, insulin, and glucagon-like peptide (GLP)-1. There were significant differences between lean and obese cats in the areas under the curve for glucose, insulin, and GLP-1. However, the responses were variable, and a clear distinction between individual lean and obese cats was not possible. Therefore, this test cannot be recommended as a routine test to examine insulin resistance in individual cats as it is used in people. A further disadvantage for routine use is also the fact that this test requires gastric tubing for the correct administration of the glucose and associated tranquilization to minimize stress and that it was associated with development of diarrhea in 25% of the cats. GLP-1 concentrations were much lower in obese than lean cats. The low GLP-1 concentrations in obese cats might indicate a contribution of GLP-1 to the lower insulin sensitivity of obese cats, but this hypothesis needs to be further investigated.  相似文献   

9.
The objective of this study was to determine if alterations in dietary intake of heifers can influence IGF-I concentrations in plasma and(or) follicular fluid (FFL), size of follicles, and steroid concentrations in FFL (as an indicator of steroidogenic capacity). Cyclic heifers [n = 23; mean +/- SE body weight (BW) = 373 +/- 7 kg] were individually fed for 10 weeks either: a) 1.8% of BW in dry matter (DM) per d (GAIN; n = 7), b) 1.1% of BW in DM per d (MAINT; n = 8) or c) 0.7% of BW in DM per d (LOSE; n = 8). After 10 wk of treatment, heifers were ovariectomized 36-40 hr after the second injection of prostaglandin F2 alpha analog (2 injections 11 d apart), and plasma and ovaries were collected. Heifers weighed 444 +/- 13,387 +/- 8 and 349 +/- 9 kg in the GAIN, MAINT and LOSE groups, respectively, at time of ovariectomy. Mean diameter of follicles greater than or equal to 10 mm was greater (P less than .05) for GAIN (15.6 mm) than for MAINT (11.0 mm) or LOSE (12.5 mm) heifers. Numbers of follicles and concentrations of IGF-I in plasma and FFL did not differ (P greater than .20) between LOSE, MAINT and GAIN heifers. Progesterone concentrations were greater (P less than .05) in small and medium follicles of GAIN than MAINT or LOSE heifers, but were unaffected by diet in large follicles. Estradiol concentrations in FFL in small, medium and large follicles were unaffected (P greater than .20) by dietary treatment.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

10.
Twelve Standardbred mares underwent blood sampling for 24 h to test the hypothesis that there is diurnal variation of humoral mediators of peripheral energy balance including active ghrelin, adiponectin, leptin, glucose, insulin, and cortisol. The experiment was conducted under acclimated conditions. Grass hay and pelleted grain were provided at 0730 and 1530. Plasma concentrations of active ghrelin and leptin concentrations both peaked (47.3 +/- 6.5 pg/ mL and 5.9 +/- 1.1 ng/mL, respectively; P < 0.05) at 1550, 20 min after feeding. Active ghrelin decreased (P < 0.05) to 28.9 +/- 4.5 pg/mL overnight. The nadir of leptin (4.6 +/- 0.9 ng/mL) occurred at 0650. Neither hormone showed variation (P > 0.05) after the morning feeding. Plasma glucose and insulin concentrations increased (P < 0.05) in response to feeding; however, the morning responses (glucose = 96.9 +/- 2.6 mg/dL; insulin = 40.6 +/- 7.3 uIU/mL) were greater (P < 0.05) than the afternoon responses (glucose = 89.9 +/- 1.8 mg/dL; insulin = 23.2 +/- 4.3 uIU/mL at 180 and 60 min after feeding, respectively). Cortisol concentrations increased (P < 0.05) during the morning hours, but did not respond to feeding, whereas adiponectin concentrations remained stable throughout the study. Hence, active ghrelin and leptin may be entrained to meal feeding in horses, whereas adiponectin seems unaffected. We concluded that there seems to be a diurnal variation in glucose and insulin response to a meal in horses. Furthermore, elevated glucose and insulin concentrations resulting from the morning feeding may be responsible for the increase in leptin concentration in the afternoon.  相似文献   

11.
The objective of this study was to evaluate, in dogs, the effects of obesity and weight loss on plasma total ghrelin and leptin concentrations. Twenty-four Beagle dogs, 12 control lean and 12 obese dogs of both genders and aged between 1 and 9 years, were used for the experiments. Mean body weight was 12.7+/-0.7 kg for the lean group and 21.9+/-0.8 kg for the obese group. The trial was divided into three phases. During phase 1, all 24 Beagle dogs were fed a maintenance diet. During phase 2, the obese dogs were submitted to a weight loss protocol with a high protein-low energy diet. The weight loss protocol ended once dogs reached optimal body weight. During phase 3, the dogs that were submitted to the weight loss protocol were maintained at their optimal body weight for 6 months. Plasma total ghrelin, leptin, insulin and glucose concentrations were measured to evaluate the effects of obesity and weight loss on these parameters in dogs. Body weight, body condition score, thoracic and pelvic perimeters, and ingested food amounts were also recorded during the study. Obese dogs demonstrated a significant decrease in plasma ghrelin and a significant increase in plasma leptin and insulin concentrations when compared with control dogs. During weight loss, significant increases in plasma total ghrelin and glucose and significant decreases in plasma leptin and insulin were observed. The increase in plasma ghrelin concentrations seemed to be transient. Body weight and the morphometric parameters correlated positively with leptin concentrations and negatively with total ghrelin concentrations. These results suggest that ghrelin and leptin could play a role in dogs in the adaptation to a positive or negative energy balance, as observed in humans.  相似文献   

12.
The prevalence of obesity is increasing in dogs as well as in humans. C-reactive protein (CRP) is an important tool for the detection of inflammation and/or early tissue damage and is linked to obesity in humans. The objective of the present study was to determine if serum CRP levels are altered in obese dogs. Fifteen lean (control group) and 16 overweight (obese group) dogs were examined. Blood samples were collected under fasted conditions for serum determination of CRP, glucose, insulin, cholesterol, triglyceride, and fructosamine. Results indicated that obese dogs were insulin resistant because serum insulin and insulin/glucose ratios were higher than in lean dogs (P < or = 0.05). Serum CRP concentrations were lower in obese dogs than in controls (P < or = 0.001). C-reactive protein was negatively correlated with insulin/glucose ratio (R = -0.42) and cholesterol (R = -0.39; P < or = 0.05). Furthermore, levels of cholesterol, triglycerides, and fructosamine were increased in the obese group compared with the control group. Based on these results, it can be postulated that CRP production is inhibited by obesity and insulin resistance in dogs.  相似文献   

13.
Influence of obesity on plasma lipid and lipoprotein concentrations in dogs   总被引：3，自引：0，他引：3  
OBJECTIVE: To determine effects of obesity and diet in dogs on plasma lipid and lipoprotein concentrations by assaying plasma leptin and ghrelin concentrations and determining total plasma cholesterol and triglyceride concentrations as well as the concentrations of cholesterol and triglycerides in various lipoprotein classes (ie, very-low-density, low-density, and high-density lipoproteins). ANIMALS: 24 Beagles; 12 lean (mean [+/- SEM] body weight, 12.7 +/- 0.7 kg) and 12 chronically obese (21.9 +/- 0.8 kg) dogs of both sexes, between 1 and 9 years old. PROCEDURES: Total plasma cholesterol and triglyceride concentrations; lipoprotein cholesterol and triglyceride concentrations; and plasma ghrelin, leptin, free fatty acids, insulin, and glucose concentrations were measured and compared between lean and obese dogs, both of which were fed a complete and balanced maintenance diet. Chronically obese dogs were subsequently fed a high-protein low-energy diet to evaluate effects of diet composition on plasma lipid and lipoprotein measurements. RESULTS: Chronic obesity resulted in a significant decrease in plasma ghrelin concentration and a significant increase in plasma leptin, cholesterol, and triglyceride concentrations in dogs. High total plasma cholesterol and triglyceride concentrations resulted from increased cholesterol and triglyceride concentrations in all lipoprotein fractions. In obese dogs, modification of diet composition resulted in beneficial effects on plasma lipid and leptin concentrations, even before weight loss was observed. CONCLUSIONS AND CLINICAL RELEVANCE: Correlations exist between obesity and plasma measurements (ie, lipoproteins, leptin, insulin, and ghrelin) commonly associated with obesity. Modification of diet composition to control energy intake improves plasma lipid and leptin concentrations in obese dogs.  相似文献   

14.
OBJECTIVE: To examine the effect of darglitazone, a compound of the thiazolidinedione class, on glucose clearance and lipid metabolism in obese cats. ANIMALS: 18 obese and 4 lean adult neutered female cats. PROCEDURE: IV glucose tolerance tests with measurements of glucose, insulin, and nonesterified fatty acid (NEFA) concentrations were performed before and 42 days after daily administration of darglitazone (9 obese cats) or placebo (9 obese and 4 lean cats). Additionally, cholesterol, triglyceride, leptin, and glycosylated hemoglobin concentrations were measured. RESULTS: Darglitazone-treated cats had significantly lower cholesterol, triglyceride, and leptin concentrations, compared with placebo-treated obese cats. A significant decrease in the area under the curve for NEFAs, glucose, and insulin during an i.v. glucose tolerance test was seen in darglitazone-treated cats. The drug was well tolerated. CONCLUSION AND CLINICAL RELEVANCE: The response of obese cats to darglitazone was similar to the response to thiazolidinediones in obese humans and rodents Darglitazone was effective in improving insulin sensitivity and glucose and lipid metabolism in obese cats.  相似文献   

15.
Intravenous glucose tolerance tests (IVGTTs) are used in cats and other species to assess insulin sensitivity. Several dosages have been reported but the dosage that maximally stimulates insulin secretion in cats has not been determined nor has it been compared in lean and obese animals. IVGTTs were performed in 4 lean and 4 obese spayed female cats with 5 glucose dosages: 0.3 (A), 0.5 (B), 0.8 (C), 1.0 (D). and 1.3 (E) g/kg body weight (BW). Each cat received each dosage in a random design. The glucose disposal rate was significantly different only between lean and obese cats at the highest glucose dosage. The area under the curve for insulin increased significantly among A, B, C, and D in lean and among A, B, and C in obese cats but not between D and E in lean and among C, D, and E in obese cats. Baseline insulin secretion was significantly higher (P = .03) and 1st peak insulin secretion was approximately 50% lower in obese as compared to lean cats (P = .03). Lean but not obese cats reached baseline insulin concentrations at all dosages at 120 minutes. We conclude that the glucose dosage for maximal insulin secretion is 1.0 g/ kg BW in lean and 0.8 g/kg BW in obese cats, supporting routine use of 1 g/kg BW to maximally stimulate insulin secretion regardless of body composition. Obese cats showed an abnormal insulin secretion pattern, indicating a defect in insulin secretion with obesity and insulin resistance.  相似文献   

16.
Two experiments were conducted to measure the effect of level of feed intake on net amino acid absorption by portal-drained viscera of six beef heifers with catheters in a mesenteric vein, portal vein and iliac artery (Exp. 1) and to evaluate intrajugular infusion of insulin or glucose on amino acid uptake by hind half of four beef steers with catheters in posterior aorta and vena cava (Exp. 2). Experiment 1 was a replicated 3 X 3 Latin square design. Treatments were calculated intakes of 84, 157 or 225 kcal metabolizable energy (ME)/kg.75 live weight. Treatments in Exp. 2 were control (no infusion), insulin infusion (1.4 IU/min for 90 min) and glucose infusion (2.5 mmol/min for 90 min) in that order. Mean live weight of animals +/- SE was 295 +/- 4 kg (Exp. 1) and 345 +/- 15 kg (Exp. 2). The diet used in both experiments was pelleted, 85% concentrate (2.9 Mcal ME/kg dry matter). Blood flow (BF) was measured by dilution of a primed, continuous infusion of para-aminohippuric acid into the mesenteric vein (Exp. 1) or the posterior aorta (Exp. 2). Net uptake or absorption was the product of BF times portal-arterial (Exp. 1) or arteriovenous (Exp. 2) differences in amino acid concentrations in blood. Increased feed intake caused linear (P less than .05) increases in net absorption of several amino acids, including lysine, methionine, leucine and valine (Exp. 1). Feed intake did not affect (P greater than .05) net absorption of glutamate or glutamine.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

17.
Two experiments were conducted to determine whether constant infusion of oxytocin would prolong the luteal phase and inhibit uterine prostaglandin F2 alpha (PGF2 alpha) secretion in heifers. In Experiment 1, twelve heifers, treated with saline (SAL) or oxytocin (OXY) via jugular cannulae infusions (INF) or osmotic minipumps (OMP), were allotted at estrus into four treatment groups (n = 3). Treatments were: SAL-INF, SAL-OMP, OXY-INF and OXY-OMP. Physiological saline or oxytocin was given from Days 10 to 23 (Day 0 = estrus) of the estrous cycle. Method of treatment (jugular cannula infusion or osmotic minipump) had no effect (P greater than 0.05) on estrous cycle length or pattern of secretion of progesterone; therefore, data were pooled. Estrous cycle lengths were extended (P less than 0.01) for heifers which received oxytocin (25.3 +/- 0.4 d) compared to saline (20.5 +/- 0.4 d). Luteolysis did not occur in oxytocin-treated heifers until after treatment ceased. Experiment 2 was designed and conducted identically to Experiment 1 with the addition of a "challenge" injection of oxytocin (100 IU oxytocin, i.v.) given on Day 16 of the estrous cycle. Treatment of heifers with oxytocin extended (P less than 0.05) estrous cycle length by an average of 3 d compared to heifers treated with saline. The "challenge" injection induced (P less than 0.05) secretion of PGF2 alpha (as measured by the stable PGF2 alpha metabolite, 15-keto-13,14-dihydro-PGF2 alpha) in saline-treated but not oxytocin-treated heifers. In both Experiment 1 and 2, serum concentrations of FSH were elevated (P less than 0.05) in oxytocin-treated heifers. No increase was observed for LH or prolactin. The rise in estradiol-17 beta at luteolysis was not affected (P greater than 0.10) by treatment. In summary, constant infusion of oxytocin extended luteal lifespan, prolonged secretion of progesterone, and inhibited oxytocin-induced secretion of PGF2 alpha. Constant infusion of oxytocin did not affect serum concentrations of estradiol-17 beta, LH or prolactin; however, serum concentrations of FSH were elevated during the oxytocin treatment period.  相似文献   

18.
The effects of acute nutritional change on endocrine and ovarian characteristics were studied in cyclic (intact; n = 20) and long-term ovariectomized (ovx; n = 18) heifers being fed 1.2 x maintenance (1.2M). On d 7 of an 8-d progesterone and estradiol treatment, intact and ovx heifers were randomly allocated to diets providing .4, 1.2, or 2.0M until emergence of the second follicular wave after ovulation in intact heifers. In intact heifers, two of eight fed .4M failed to ovulate. In the other six, growth rate and maximum diameter (1.1+/-.09 mm/d and 10.1+/-.7 mm, respectively) of the first dominant follicle (DF) postovulation were less (P<.05) than in heifers fed either 1.2 (1.6+/-.18 mm/d; 12.9+/-.44 mm) or 2.0M (1.6+/-.08 mm/d; 12.7+/-.7 mm). In intact heifers, LH pulse frequency and amplitude were not affected by diet (P>.10). In ovx heifers, the frequency of LH pulses was unaffected by diet (P>.10), but heifers fed .4M had a greater pulse amplitude (P<.05) and mean concentration of LH (P<.001) than those fed 1.2 or 2.0M. Plasma concentrations of FSH were greater (P<.05) in ovx heifers fed .4M than in those fed 1.2 or 2.0M and increased linearly with time (P<.01). The FSH concentrations in heifers fed 1.2 and 2.0M were similar (P>.10) and decreased linearly with time (P<.001). In intact heifers, concentrations of FSH preceding follicle wave emergence were greater in heifers fed .4M (P<.001), but basal concentrations were not affected (P>.10). Concentrations of progesterone and estradiol were unaffected by diet (P>.10). Significant diet x ovarian status interactions in plasma IGF-I concentrations existed. Plasma concentrations of insulin increased as the level of nutrition increased, whereas concentrations of NEFA decreased. In conclusion, growth rate and maximum diameter of the DF were decreased by acute nutritional restriction, without affecting the concentration of LH. The magnitude of the FSH increase preceding new follicle wave emergence increased following dietary restriction, but concentrations of FSH were unaffected during the other stages of DF growth. The results of this study may have important implications for the feeding strategies adapted for high-yielding dairy cows in the early postpartum period when feed intake is often physiologically restricted.  相似文献   

19.
To determine the effect of the hyperadrenal state on corpus luteum (CL) function, we treated intact and adrenalectomized (ADRX) heifers with adrenocorticotropin (ACTH) and hydrocortisone. ACTH treatment of intact heifers by infusion of 1 mg alpha 1-24 ACTH/24 hr from day 2 to 25 of an estrous cycle increased progesterone concentrations in plasma to 4 +/- .52 ng/ml plasma on days 3 to 4. Thereafter, progesterone concentrations declined, indicating severe suppression of CL function as compared to that of control heifers. Similar infusions of ACTH to ADRX heifers did not alter CL function as reflected by progesterone concentrations in jugular plasma. Infusion of ADRX animals with hydrocortisone succinate (100 mg/24 hr) decreased progesterone in plasma during the cycle, with maximum values averaging less than 4 ng/ml, compared to concentrations of 6 to 7 ng/ml in control ADRX heifers. Chronic administration of ACTH or hydrocortisone to heifers caused a decreased progesterone secretion during the luteal phase of the estrous cycle. On the basis of these results, we suggest that stress, as indicated by the hyperadrenal state, could inhibit progesterone secretion by the corpus luteum.  相似文献   

20.
The prevalence of feline diabetes mellitus has increased several-fold over the last three decades. In humans, progression from obesity to diabetes is marked by changes in the release of proinsulin. A specific proinsulin (FPI) assay has not been available to examine similar changes in cats. The goal of this study was to develop a proinsulin assay for the analysis of beta cell function in cats. Monoclonal antibodies were developed against recombinant FPI and used in a two-site sandwich immunoradiometric assay (IRMA) and enzyme-linked immunosorbent Assay (ELISA). The antibody pair had negligible cross-reactivity with bovine insulin and feline C-peptide. The working range was 11-667pmol/L for the IRMA and 11-1111pmol/L for the ELISA. An intravenous glucose tolerance test was performed in six long-term obese and six lean adult healthy cats and serum glucose, insulin, and FPI concentrations were determined. The proinsulin and insulin secretion pattern in response to glucose was significantly different between lean and obese cats but the pattern was similar within a group. Both groups had similar baseline proinsulin/insulin ratios; however, obese cats showed a significantly higher proinsulin/insulin ratio during the first 15min of the IVGTT and a much lower ratio during the last 30min suggesting a time-delayed adjustment to the increased insulin demand. In conclusion, we report the development and validation of an IRMA and an ELISA for FPI. This novel assay is useful to elucidate FPI secretion and can be used similar to a C-petide assay to evaluate residual beta cell function in cats.  相似文献   

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