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1.
The aim of the present study was to investigate the changing profiles of plasma metabolic hormones during the ovarian cycles of beef and dairy cattle. We used 16 non-pregnant, non-lactating Japanese Black beef cattle (6 heifers and 10 cows; parity=2.3 +/- 0.8) and 12 multiparous Holstein dairy cows (parity=3.0 +/- 0.3). Blood samples for hormonal analysis (growth hormone, GH; insulin-like growth factor-I, IGF-1; insulin; and progesterone, P4) were obtained twice weekly for 40 days before artificial insemination for Japanese Black cattle and from 50 to 100 days postpartum for Holstein cows. Luteal phases were considered normal if the P4 concentrations for at least 3 time points over the course of 7 days remained above 1 ng/ml and at least 2 of the time points were above 2 ng/ml. The patterns of the ovarian cycles were classified into two types (normal or abnormal, such as having prolonged luteal phase and cessation of cyclicity) on the basis of the plasma P4 profiles. The plasma concentrations of IGF-1 in both breeds increased transiently during the preovulatory period when the P4 levels were low and decreased to lower levels during the luteal phase when the P4 levels were high. The plasma concentrations of insulin in the 3(rd) week of normal ovarian cycles when the plasma P4 concentration dropped to less than 1 ng/ml were higher than those at other time points in the Japanese Black cattle, but not in the Holstein cows. The plasma concentrations of GH did not change during the ovarian cycle in either breed. In conclusion, the present study indicates that the plasma IGF-1 concentration increases during the follicular phase (low P4 levels) and decreases during the luteal phase (high P4 levels) in non-lactating Japanese Black and lactating Holstein cattle. The results suggest that ovarian steroids, rather than nutrient status, may be related to the cyclic changes in IGF-1 secretion from the liver in cattle.  相似文献   

2.
Concentrations of plasma glucose, immunoreactive insulin (IRI) and free fatty acid (FFA) and activities of enzymes related to energy metabolism and lactate dehydrogenase (LDH) isoenzyme pattern in plasma and leukocytes were investigated in lactating Holstein cows (dairy cattle) and fattening Japanese Black Wagyu x Holstein steers (beef cattle). IRI concentrations and LDH and malate dehydrogenase (MDH) activities in the plasma of beef cattle were significantly higher than those in dairy cattle. The cytosolic ratio of MDH/LDH activity in the leukocytes of beef cattle was significantly higher than that of dairy cattle. These findings might be associated with the different energy metabolism between dairy and beef cattle.  相似文献   

3.
OBJECTIVE: To determine the insulin response curve during IV glucose tolerance testing of mature Holstein bulls. ANIMALS: 8 Holstein bulls between 5 and 8 years old and weighing between 911.5 and 1035.5 kg. PROCEDURE: A 50% glucose solution was rapidly administered IV so that each bull received a mean dose of 258 mg of glucose/kg of body weight. Serum glucose and insulin concentrations were determined before and 30, 60, 120, and 240 minutes after glucose infusion. RESULTS: Serum glucose concentrations 30 and 60 minutes after infusion were significantly greater than baseline concentration. Concentrations returned to baseline values 120 minutes after infusion. Serum insulin concentration was significantly greater 30 minutes after glucose administration, compared with baseline and 240-minute concentrations. CONCLUSIONS AND CLINICAL RELEVANCE: Intravenous glucose tolerance testing of mature Holstein bulls resulted in a characteristic insulin response curve. Baseline and peak insulin concentrations were higher in these bulls, compared with values reported for mature Norwegian Red cows.  相似文献   

4.
This study determined if the insulin and glucose responses to glucose infusion in obese (n = 4) and lean (n = 4) Holstein heifers were affected by stage of the estrous cycle. Glucose (.35 g/kg) was infused within 2 min into the jugular veins of heifers during diestrus (d 15) and at the subsequent estrus (d 0). Concentrations of insulin and glucose were determined in jugular venous serum obtained from blood samples collected at 60, 45, 30, 15 and 1 min before and at 2.5, 5, 10, 15, 20, 30, 40, 50, 60, 80, 100, 120, 140, 160, 180, 210 and 240 min after glucose. Mean (+/- SE) pretreatment concentrations of glucose (mg/100 ml) in obese (68 +/- 1.9) and lean (71 +/- 2.5) heifers were unaffected by body condition and stage of the cycle. Mean (+/- SE) pretreatment concentrations of insulin (microU/ml) were unaffected by stage of the cycle but were higher (P less than .05) in obese (33 +/- 3.6) than in lean (18 +/- 2.7) heifers. Body condition affected the insulin response with greater absolute concentrations (P less than .01) and total (P less than .005) response areas of insulin in obese than in lean heifers. Kinetics of the injected glucose were unaffected by body condition and stage of the cycle.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

5.
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   

6.
Twenty mature, lactating Hereford-cross cows were used to determine the effect of phlorizin-induced hypoglycemia on gonadotropin secretion following prostaglandin-induced luteolysis. Cows were 43 to 108 d postpartum and had a functional corpus luteum (CL) at the start of infusion treatment (d 1). Infusions consisted of either saline (control) or 3 g/d of phlorizin infused continuously from the time of prostaglandin injection at 1000 on d 1 until 0800 on d 5. Blood samples were collected for determination of plasma concentrations of insulin, glucose and free fatty acids (FFA) and for serum concentrations of luteinizing hormone (LH), follicle-stimulating hormone (FSH) and progesterone. Plasma concentrations of insulin (P less than .05) and glucose (P less than .05) were lower, whereas FFA concentrations increased (day X treatment, P less than .05) over the infusion period in phlorizin-treated cows compared with saline-infused controls. Mean serum concentrations of LH (1.17 +/- .10 vs 1.53 +/- .20 ng/ml; P less than .05) and LH pulse amplitude (1.69 +/- .14 vs 2.47 +/- .37 ng/ml; P less than .10) were lower in phlorizin-infused compared with saline-infused cows during the 0 to 24-h period immediately preceding the ovulatory gonadotropin surge. The FSH pulse frequency increased (.33 +/- .11 to .55 +/- .12 pulses/h) in saline-infused cows, but decreased (.61 +/- .10 to .41 +/- .11 pulses/h) in phlorizin-infused cows before the gonadotropin surge. Other characteristics of gonadotropin secretion were similar among phlorizin-infused and saline-infused cows. All but one phlorizin-infused cow ovulated and formed functional CL similar to controls.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

7.
Intravenous administration of xylazine to beef cattle (10 animals, 0.2 mg/kg of body weight) resulted in rapid onset (less than 15 minutes) of hyperglycemia. Plasma glucose values increased to 195 +/- 15 mg/dl and 305 +/- 10 mg/dl at 15 minutes and 3 hours, respectively. Concomitantly, plasma insulin concentrations dropped from 23 +/- 2 microU/ml before xylazine to 5.8 +/- 0.7 microU/ml and 2.4 +/- 0.3 microU/ml at 15 minutes and 3 hours, respectively. Parallel decreases (20%) were observed for percentage of hemoglobin, red blood cell number, and packed cell volume. Plasma urea nitrogen was significantly (P less than 0.01) incrased within 3 hours of xylazine administration (6.7 +/- 0.9 mg/dl vs 11.4 +/- 0.7 mg/dl). Marked changes in concentrations of plasma-free fatty acids were not observed. Alternative means of anesthesia must be considered in those instances in which biopsy material is to be used for studies of carbohydrate metabolism in vitro.  相似文献   

8.
OBJECTIVE: To determine the effect of continuous IV administration of 50% dextrose solution on phosphorus homeostasis in lactating dairy cows. DESIGN: Clinical trial. ANIMALS: 4 multiparous Jersey cows. PROCEDURES: Cows were administered 50% dextrose solution IV (0.3 g/kg/h [0.14 g/lb/h]) for 5 days. Plasma concentrations of glucose, immune-reactive insulin (IRI), and phosphorus were determined before, during, and for 72 hours after dextrose infusion. Phosphorus intake and losses of phosphorus in urine, feces, and milk were determined. Each cow received a sham treatment that included instrumentation and sampling but not administration of dextrose. RESULTS: Plasma glucose, IRI, and phosphorus concentrations were stable during sham treatment. Plasma phosphorus concentration decreased rapidly after onset of dextrose infusion, reaching a nadir in 24 hours and remaining less than baseline value for 36 hours. Plasma phosphorus concentration increased after dextrose infusion was stopped, peaking in 6 hours. Urinary phosphorus excretion did not change during dextrose infusion, but phosphorus intake decreased because of reduced feed intake, followed by decreased fecal phosphorus loss and milk yield. Rapid changes in plasma phosphorus concentration at the start and end of dextrose infusion were temporally associated with changes in plasma glucose and IRI concentrations and most likely caused by compartmental shifts of phosphorus. CONCLUSIONS AND CLINICAL RELEVANCE: Hypophosphatemia developed in response to hyperglycemia or hyperinsulinemia in dairy cows administered dextrose via continuous IV infusion. Veterinarians should monitor plasma phosphorus concentration when administering dextrose in this manner, particularly in cows with decreased appetite or preexisting hypophosphatemia.  相似文献   

9.
OBJECTIVE: To determine blood glucose clearance in 2 species of New World camelids after IV challenge and to examine mechanisms of this clearance. ANIMALS: 5 adult female llamas and 5 adult gelded alpacas. PROCEDURE: After food was withheld for 12 hours, camelids received 0.5 g of glucose/kg of body weight by rapid IV infusion. Serum concentrations of glucose, nonesterified fatty acids, cortisol, and insulin, and plasma concentrations of lactate were determined before and 0, 1, 2, 3, 4, 5, 15, 30, 60, 90, 120, 180, and 240 minutes after infusion. Ratios of insulin to glucose and insulin to cortisol were calculated for each time point. RESULTS: Postinfusion glucose concentrations were significantly higher in llamas than alpacas for the first 15 minutes and remained significantly higher than baseline values in both species for 180 minutes. Lactate and cortisol concentrations did not change significantly; nonesterified fatty acid concentrations decreased in both species 30 minutes after infusion. Baseline insulin concentrations were < 6 microU/ml in both species and increased only to 10.1 +/- 0.7 microU/ml in llamas. Insulin concentrations did not change significantly in alpacas. CONCLUSIONS AND CLINICAL RELEVANCE: Llamas and alpacas clear glucose more slowly than other domestic species after challenge, mainly because of a weak insulin response and slow cellular uptake. This response may impair the assimilation of exogenous glucose as well as make llamas and alpacas prone to diabetes-like disorders when an abundance of endogenous or exogenous glucogenic agents are present.  相似文献   

10.
Pituitary adenylate cyclase-activating polypeptide (PACAP) is a hypothalamic neuropeptide that stimulates release of growth hormone (GH) from cultured bovine anterior pituitary gland cells, but the role of PACAP on the regulation of in vivo secretion of GH in cattle is not known. To test the hypothesis that PACAP induces secretion of GH in cattle, meal-fed Holstein steers were injected with incremental doses of PACAP (0, 0.1, 0.3, 1, 3, and 10 microg/kg BW) before feeding and concentrations of GH in serum were quantified. Compared with saline, injection of 3 and 10 microg PACAP/kg BW increased peak concentrations of GH in serum from 11.2 ng/ml to 23.7 and 21.8 ng/ml, respectively (P < 0.01). Peak concentrations of GH in serum were similar in steers injected with 3 or 10 microg PACAP/kg BW. Meal-fed Holstein steers were then injected with 3 microg/PACAP/kg BW either 1 hr before feeding or 1 hr after feeding to determine if PACAP-induced secretion of GH was suppressed after feeding. Feeding suppressed basal concentrations of GH in serum. Injection of PACAP before feeding induced greater peak concentrations of GH in serum (19.2 +/- 2.6 vs. 11.7 +/- 2.6 ng/ml) and area under the response curve (391 +/- 47 vs. 255 +/- 52 ng. ml(-1) min) than injection of PACAP after feeding, suggesting somatotropes become refractory to PACAP after feeding similar to that observed by us and others with growth hormone-releasing hormone (GHRH). We concluded that PACAP induces secretion of GH and could play a role in regulating endogenous secretion of GH in cattle, perhaps in concert with GHRH.  相似文献   

11.
We measured changes in plasma ghrelin and GH concentrations in mature Holstein cows and 3-mo-old female Holstein calves fed at scheduled times. Our objective was to determine the characteristics of ghrelin secretion in dairy cattle and its influence on GH. Animals were fed at 0800 and 1600 for 2 wk before and during experiments. Plasma was sampled for 24 h at 2-h intervals in Exp. 1. In mature cows, plasma ghrelin concentrations decreased (P < 0.01) just after 0800 but not at the 1600 feeding. Ghrelin concentrations were lower (P < 0.01) in calves than in mature cows and they did not decrease after feeding in calves. The temporal relationship between ghrelin and GH remained unclear. In Exp. 2, plasma was sampled 2 h before and after both morning and evening feedings at 20-min intervals. Plasma ghrelin concentrations decreased (P < 0.05) 40 min after 0800 feeding and 60 min after 1600 feeding in mature cows. These results indicate that in mature cows, plasma ghrelin concentration decreased after feeding, but this decrease was not evident in 3-mo-old calves. Further studies are required to define the relationship between plasma ghrelin and GH concentrations.  相似文献   

12.
Plasma insulin-like growth factor-I (IGF-I) concentrations were monitored in Holstein females through different periods of their growth, lactation and after acute or chronic growth hormone-releasing factor (GRF) administration. Plasma samples were radioimmunoassayed using a human IGF-I antibody after a 24 hr incubation in a HCl(.1N)-glycine(.2M) buffer (pH 2). In a first study, IGF-I concentrations were measured in Holstein females of different ages and(or) stages of lactation (n = 6 per group). The IGF-I concentrations in newborn calves (102.0 +/- 11.3 ng/ml) markedly decreased (P less than .01) in 1 mo old animals (50.2 +/- 7.1 ng/ml), then increased (P less than .01) to 137.0 +/- 5.1 and 137.4 +/- 11.0 ng/ml in 6 and 10 mo old heifers, respectively. In dairy cows, IGF-I concentrations were low 24 hr post-partum (44.7 +/- 7.6 ng/ml) and then increased (P less than .05) to remain stable throughout lactation (91.3 +/- 4.9, 92.8 +/- 12.9, 96.1 +/- 7.6, 90.7 +/- 8.8 ng/ml at 2, 3, 6 and 9 mo of lactation, respectively). There was a further increase (P less than .05) to 113.7 +/- 3.1 ng/ml during the dry period. In a second trial, blood samples were collected from lactating dairy cows every 2 hr for 24 hr following a sc injection of saline (n = 4) or human (h) GRF (1-29)NH2 (10 micrograms/kg BW, n = 4). The IGF-I peak concentration was reached on average 10 hr after the GRF injection and was higher (P less than .01) in treated cows than in control cows (135.4 vs 86.9 +/- 16.2 ng/ml). In the last trial, daily sc injections of 10 micrograms of hGRF(1-29)NH2 per kg BW to dairy cows (252 days of lactation) for 57 days, which increased milk production by 14% (2 kg/day), also increased (P less than .01) IGF-I concentration: 127.1 +/- 5.3 and 118.0 +/- 1.6 vs 90.7 +/- 4.7 and 96.0 +/- 5.0 ng/ml on days 29 and 57 of treatment for treated (n = 9) and control (n = 8) cows, respectively. Thus, the IGF-I concentration in dairy cattle varies with age and stage of lactation, and is increased by GRF administration in lactating dairy cows.  相似文献   

13.
The absorption kinetics of porcine regular insulin following IV, IM, and SC administration were evaluated in 10 dogs with alloxan-induced diabetes mellitus. Plasma immunoreactive insulin (IRI) concentrations were evaluated immediately prior to and at 10, 20, 30, 45, 60, 90, 120, 180, and 240 minutes following IV administration; and immediately prior to and every 30 minutes for 2 hours and then every hour for 6 hours following IM and SC administration of 0.55 U of porcine regular insulin/kg of body weight. Model-independent pharmacokinetic analysis was performed on each data set. Plasma IRI concentration declined rapidly after IV administration of regular insulin and then returned to baseline IRI concentration by 3.2 +/- 0.8 hours. The absorption kinetics following IV administration of regular insulin were similar to those found in earlier studies in healthy dogs and human beings. The IM and SC routes of regular insulin administration resulted in a pharmacologic concentration of IRI at 30 minutes. The peak mean (+/- SD) plasma IRI concentration was significantly (P less than 0.05) greater following SC administration than it was following IM administration of regular insulin (263 +/- 185 and 151 +/- 71 I microU/ml, respectively). The time of the peak plasma IRI concentration (68 +/- 31 minutes and 60 +/- 30 minutes) and the time to return to baseline plasma IRI concentration (5.8 +/- 1.2 hours and 5.8 +/- 1.3 hours) were not significantly different following SC and IM administration of regular insulin, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

14.
We determined the effects of short-term fasting and refeeding on temporal changes in plasma concentrations of leptin, insulin, insulin-like growth factor- 1 (IGF-1), growth hormone (GH), glucose, and nonesterified fatty acids (NEFA), in early lactating cows, non-lactating pregnant cows, and postpubertal heifers. In experiment 1, Holstein cows in early lactation were either fed ad libitum (Control, n=5) or feed deprived for 48 h (Fasted, n=6). Plasma leptin, insulin, and glucose concentrations rapidly declined (P<0.05) within 6h, and IGF-1 by 12h, but all these variables sharply returned to control levels (P>0.10) within 2h of refeeding. Plasma NEFA and GH concentrations were elevated (P<0.05) by 4 and 36 h of fasting and returned to control levels (P>0.10) by 8 and 24h after refeeding, respectively. In experiment 2, four ruminally cannulated pregnant non-lactating Holstein cows were used in a cross-over design and were fasted for 48 h (Fasted) or fasted with partial evacuation of rumen contents (Fasted-Evac). The plasma variables measured did not differ (P>0.10) between Fasted and Fasted-Evac cows. Plasma leptin, insulin, and IGF-1 concentrations were reduced by 10, 6, and 24h of fasting, respectively, in Fasted-Evac cows; and these variables were reduced by 24h in Fasted cows (P<0.05). Plasma glucose levels were reduced (P<0.05) by 48 h of fasting in both groups of fasted animals. Plasma NEFA and GH levels were increased (P<0.05) by 12 and 48 h of fasting, respectively. In experiment 3, postpubertal Holstein heifers were either fed ad libitum (Control, n=4) or feed deprived for 72 h (Fasted, n=5). Concentrations of leptin, insulin, IGF-1, and glucose in plasma were reduced (P<0.05) by 24, 10, 24, and 48 h of fasting, respectively. Plasma NEFA concentrations increased (P<0.05) by 4h, of fasting while GH levels were not significantly (P>0.10) affected by fasting. Collectively, our data provide evidence that plasma leptin concentrations are reduced with short-term fasting and rebound on refeeding in dairy cattle with the response dependent on the physiological state of the animals. Compared to the rapid induction of hypoleptinemia with fasting of early lactation cows, the fasting-induced hypoleptinemia was delayed in non-lactating cows and postpubertal heifers.  相似文献   

15.
Early (EL) and late (LL) lactation Holstein cows were segregated into three Cow Index (CI) groups (high, HG; medium, MG; low, LG; n = 47). Feed intake by lactation group, individual milk yield data and blood samples, obtained by puncture of the coccygeal vein or artery at 12-hr intervals, were collected for 7 d. Cows were fed alfalfa hay top dressed with grain mixture. On day 7, 5 g of subcutaneous adipose tissue were removed from the tail-head region. Tissue was minced into 10-15 mg pieces in Krebs-Ringer bicarbonate buffer with 5 ng/ml insulin added (KRB). Triplicate 100-mg aliquots were incubated in KRB + 3% essentially fatty-acid-free bovine serum albumin with either 50 ng/ml growth hormone (G), 5 micrograms/ml epinephrine (EPI), both (G+E) or neither (CON) at 37 C for 2 hr. Early lactation cows averaged greater (P less than .05) daily milk production (33.4 vs 22.1 kg), greater (P less than .05) plasma growth hormone (GH) concentrations (3.9 vs 3.0 ng/ml) but lesser (P less than .01) insulin (INS) concentrations (.49 vs .73 ng/ml) than LL cows. Adipose tissue FFA release in vitro was greater (P less than .01) when media contained EPI (EPI: 8.10; G+E: 8.05 microE/l/g tissue) than when EPI was not present (CON: 1.33; G: 1.39 microE/l/g tissue), but was not affected by stage of lactation. Including hormonal data in the model as covariates indicated that increased plasma INS concentrations before biopsy reduced subsequent FFA release in vitro when tissue was incubated with added EPI, but not when incubation media lacked EPI. Increased GH concentrations had the opposite effect. Further, FFA release was greatest from HG cow adipose when incubated in media lacking EPI, but greatest from LG cow adipose when incubated in media containing EPI.  相似文献   

16.
The article describes the dynamics of changes in blood concentrations of the active substances present in the solution after its infusion to healthy cows in comparison to NaCI solution as well as the response of paretic cows to treatment with the new complex solution. Cows received a dose of 400 ml of A1 solution (containing 8.4 g of Ca2+) intravenously. In healthy cows the average calcium concentration in blood serum prior to the test was 2.52 +/- 0.08 mmol/l while 15 min. after the infusion the concentration rose to 3.10 +/- 0.08 mmol/l (p < 0.05) and magnesium concentration rose from 0.61 +/- 0.05 to 1.39 +/- 0.08 mmol/l (p < 0.05). This experiment showed that elevated concentration of non-organic phosphates persisted 1 hour after infusion (p < 0.05). In the second phase of efficacy evaluation of the novel preparation A1 on paretic cows the intravenous injection of 1 ml/kg of body weight of A1 solution increased calcium concentration up to almost normal level (p < 0.05). The level of magnesium in serum 1 h after injection was statistically significantly higher by 63% (p < 0.05) and reached the physiologically normal concentration. 1 h after the infusion of test solution the level of phosphate was higher by 13% (p > 0.05). The rise was statistically not significant. Even though A1 solution undoubtedly produced an increase in glucose concentration in the blood serum, due to wide dispersion of individual measurements and high standard deviation the increase (p > 0.05) in glucose concentration was found insignificant. Most of the treated paretic cows rose within 1-6 h after infusion of 400 ml of solution A1. No relapses were observed. A combination of different salts of calcium and magnesium, non-organic phosphates and glucose with analeptic substance mixed in one solution (A1 solution) administered at a dose of 1 ml/kg of body weight raises concentrations of essential macroelements in blood serum of cattle and promotes improvement of paretic cows condition.  相似文献   

17.
To determine whether there is a day-to-day variation in insulin sensitivity in cats, we subjected six clinically normal cats to four insulin-modified frequently sampled intravenous glucose tolerance tests (FSIVGTTs) over 7 days. The insulin-modified FSIVGTTs were analysed by the minimal model method. Minimal model insulin sensitivity (S(I)) averaged 2.9+/-0.4 x 10(-4) min(-1)/microU/ml (range 1.9-4.6 x 10(-4) min(-1)/microU/ml), with a mean interday coefficient of variation (CV) of 35.4+/-6.4% (range 12.8-58.5%). Glucose effectiveness (S(G)) averaged 0.029+/-0.002 min(-1)(range 0.024-0.037 min(-1)), and showed less interday variability with a mean CV of 24.7+/-4.3% (range 7.9-39.3%). Insulin sensitivity was also measured after a short-term stressor (5-min spray bath) of sufficient magnitude to elevate blood glucose levels. The mean insulin sensitivity after the stressor was 3.6+/-0.8 x 10(-4) min(-1)/microU/ml (range 1.6-7.3 x 10(-4) min(-1)/microU/ml), which was not significantly different to the mean insulin sensitivity before the short-term stressor (P=0.237). The mean glucose effectiveness after the stressor was 0.046+/-0.004 min(-1)(range 0.032-0.057 min(-1)), which was significantly different from mean glucose effectiveness before the short-term stressor (P=0.003). We conclude that insulin sensitivity is highly variable from day to day in normal cats, and that hyperglycaemia in response to short-term stressors is probably due to increased hepatic glucose production, rather than peripheral insulin resistance.  相似文献   

18.
To investigate the effects of amino acids on ghrelin‐induced growth hormone (GH), insulin and glucagon secretion in lactating dairy cattle, six Holstein cows were randomly assigned to two infusion treatments in a cross‐over design. Mixture solution of amino acids (AMI) or saline (CON) was continuously infused into the left side jugular vein via catheter for 4 h. At 2 h after the start of infusion, synthetic bovine ghrelin was single injected into the right side jugular vein through the catheter. Ghrelin injection immediately increased plasma GH, glucose and non‐esterified fatty acids (P < 0.05) with no difference between both treatments. Additionally, plasma insulin and glucagon concentrations were increased by ghrelin injection in both treatments. The peak value of plasma insulin concentration was greater in AMI compared with CON (P < 0.05). Plasma glucagon concentration showed no difference in the peak value reached at 5 min between both treatments, and then the plasma levels in AMI compared with CON showed sustained higher values (P < 0.05). After plasma glucose concentration reached the peak, the decline was greater in AMI compared with CON (P < 0.05). These results showed that the increased plasma amino acids may enhance ghrelin action which in turn enhances insulin and glucagon secretions in lactating cows.  相似文献   

19.
Plasma concentrations of prolactin (PRL), growth hormone (GH), insulin, glucagon, glucose, urea and free fatty acids (FFA) were measured in Holstein calves, yearlings, bred heifers and primiparous cows, either sired by bulls with high predicted differences (PD) for milk (selection group) or by bulls from an unselected random bred control population (control group; n = 6). Serial blood samples were collected before and after feeding for an 8-h period from 0900 to 1700 h. All animals were fed a complete feed at 1100 h and administered insulin (.6 IU/100 kg body weight) at 1400 h. Mean plasma PRL was greater in control animals after feeding and insulin administration, while GH was greater overall in selection cattle. Insulin remained elevated longer in selection animals after exogenous administration, and plasma glucagon was increased in the control group. While plasma glucose and urea were unaffected by genetic group, plasma FFA were elevated in selection group calves and primiparous cows compared with the control group. All hormones and metabolites differed among the pre- and post-feeding and insulin administration periods and also with age. Mean PRL and GH increased after feeding, while glucagon decreased after exogenous insulin. Plasma FFA declined after feeding, while urea and glucose were similar before and after feeding. Mean PRL increased and glucagon decreased with advancing age and plasma GH and insulin showed inverse relationships at different ages. Plasma FFA changes closely followed GH changes with age, while plasma glucose more closely followed insulin changes with age. Results indicate that all hormones measured and FFA responded to genetic selection for milk, and increases in GH are uniformly associated with increased genetic potential for milk yield.  相似文献   

20.
Growth hormone secretion was evaluated in cattle. Clinically healthy bovine growth hormone (bGH) concentrations were 10.7 +/- 1.6 ng/ml in Holstein and 7.8 +/- 3.9 ng/ml in Japanese black cattle. The bGH concentration alternated at three-hour intervals, and tended to be higher at midnight and lower in the morning and before feeding. Insulin tolerance test (ITT) at an insulin dosage of 0.25 U/kg showed a significant increase of bGH concentration to 331 +/- 153% at 60 to 90 min after injection. In ITT applied to five under-growth calves of Japanese black cattle, the basal bGH concentrations were lower and peak values after insulin injection were shown to be significantly low. The ITT is useful for the clinical examination of bGH secretion in cattle.  相似文献   

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