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1.
Severe hypoxia during birth results in a metabolic acidosis and depressed heat production capacity. The aetiology of the depressed heat production capacity is unknown. To investigate this problem newborn lambs were exposed to a 30 minute period of hypoxia by causing them to breathe room air diluted with nitrogen. Heat production capacity was subsequently estimated as summit metabolic rate. When summit metabolic rate was estimated at the end of the period of hypoxia a depression to 66 per cent of the control value was observed (P less than 0.01) but no depression was observed when the estimation of summit metabolic rate was delayed for 30 minutes. Hypoxia resulted in metabolic acidosis, hyperlactaemia and considerable increases in the plasma concentrations of adrenaline and noradrenaline. Summit metabolic rate was positively correlated with blood pH at the beginning of summit metabolism in lambs which had a pH value of less than 7.05. There were no other relationships between summit metabolic rate and blood composition. These results suggest that the poor heat production capacity found in lambs which have suffered hypoxia during birth may be directly related to acidaemia.  相似文献   

2.
The intensity and duration of exercise exert a major influence on energy expenditure and physiological changes in the horse. Stressful environmental conditions, acclimation, and training status may further modify these responses. To maintain functional homeostasis during exercise, changes in autonomic nervous activity and hormone secretion are coupled to both the feedforward and the feedback mechanisms that control substrate mobilisation and utilisation.During exercise, both the sympathetic nervous system and the hypothalamic-pituitary-adrenal axis are activated, which increases the circulating levels of adrenocorticotropin (ACTH), cortisol, adrenaline and noradrenaline. Furthermore, adrenaline inhibits the release of insulin from the pancreas. Catecholamines, adrenaline, and noradrenaline increase glycogen breakdown in the muscles. In the liver, catecholamines, together with cortisol, increase blood glucose by activating glycogen breakdown and gluconeogenesis. Cortisol and catecholamines also enhance the mobilisation of free fatty acids from fat stores.In addition to efficient energy metabolism, the ability to exercise is highly dependent on the well-coordinated neuroendocrine control of cardiovascular function. Catecholamines increase oxygen delivery during exercise by enhancing cardiac output, splenic erythrocyte release, and skeletal muscle flow. Furthermore, cardiovascular homeostasis is maintained by changes in plasma renin activity and in plasma concentrations of atrial natriuretic peptide (ANP), arginine vasopressin, and aldosterone.  相似文献   

3.
Nine Thoroughbred horses were assessed to determine the normal response of insulin, glucose, cortisol, plasma potassium (K) and erythrocyte K through conditioning and to exercise over 400 and 1,000 m. In addition, adrenaline, noradrenaline, cortisol, plasma K, erythrocyte K and L-lactate concentrations were evaluated in response to maximal exercise with and without the administration of acepromazine. Conditioning caused no obvious trends in plasma K, erythrocyte K, insulin or glucose concentration. Serum cortisol increased (P less than 0.05) from the initial sample at Week 1 to Weeks 4 and 5 (attributed to a response to training), and then decreased. During conditioning, three horses had low erythrocyte K concentrations (less than 89.3 mmol/litre). Further work is needed to define the significance of low erythrocyte K concentrations in the performance horse. In all tests maximal exercise increased plasma K, glucose and cortisol concentrations, whereas insulin and erythrocyte K concentrations decreased. Thirty minutes following exercise, plasma K and erythrocyte K concentrations returned to resting values; whereas glucose and cortisol concentrations continued to increase and the insulin concentration also was increased. The magnitude of the changes varied for pre-conditioned vs post-conditioned exercise tests and the duration of exercise. The administration of acepromazine prior to exercise over 1,000 m failed to alter the circulating noradrenaline and adrenaline concentrations in anticipation of exercise or 2 mins following exercise. Acepromazine administration, however, did cause lower L-lactate concentration 2 mins (P less than 0.03) and 30 mins (P less than or equal to 0.005) following exercise. Also, erythrocyte K showed a delayed return to baseline levels at 30 mins post exercise. Further evaluation of these trends may help explain the beneficial role acepromazine plays in limiting signs of exertional rhabdomyolysis when administered prior to exercise.  相似文献   

4.
Prolonged infusions of bacterial lipopolysaccharides (LPS) are known to model gram-negative bacterial infections, but the basic mechanisms of the LPS effects on feed intake and metabolism and their potential interdependence are largely unknown. The aim of the present study was to distinguish and to better characterize the feeding suppressive and metabolic effects of LPS. Six heifers were infused intravenously for 100 min with either 1) LPS (2 microg/kg BW) with free access to feed, 2) saline with free access to feed, or 3) saline with feeding restricted to the amount of feed consumed after LPS infusion. Feed intake, body temperature, plasma concentrations of various metabolites and hormones, and the respiratory quotient and heat production were measured. The LPS reduced feed intake and induced pronounced changes in metabolic energy turnover and fat and carbohydrate metabolism that were largely independent of the concomitant feed intake reduction. Some of the metabolic changes were biphasic; the first phase resembled a stress response with increases in plasma glucose and cortisol, and the second phase reflected a beginning energy deficit with low plasma glucose and enhanced lipolysis. The coincidence of a short-term surge of plasma insulin with marked transient decreases in plasma FFA, glycerol, and beta-hydroxybutyrate as well as with the transition from hyper- to hypoglycemia indicates that insulin plays a role in some of the metabolic responses to LPS. The failure of LPS to clearly increase energy expenditure despite the increase in body temperature suggests that anaerobic mechanisms of heat production and, perhaps, a reduced peripheral blood flow contributed to the fever. Many of the initial metabolic responses occurred before and, therefore, independent of, an increase in circulating tumor necrosis factor-alpha.  相似文献   

5.
AIM: To compare the changes in plasma concentrations of noradrenaline, adrenaline and cortisol in lambs after ring castration plus tailing and in calves after dehorning with or without prior local anaesthesia. METHODS: Male lambs were castrated and tailed with rings and calves were dehorned by amputation using a scoop with or without prior local anaesthesia. Blood samples were taken before and after treatment and plasma concentrations of noradrenaline, adrenaline and cortisol were determined. RESULTS: Castration plus tailing of lambs resulted in a rapid increase in noradrenaline concentrations, a lack of an adrenaline response and a marked increase in cortisol concentration. There were similar changes in catecholamine concentrations in calves that were dehorned both with and without local anaesthetic, with adrenaline being elevated within 5 min of treatment and noradrenaline exhibiting a more protracted response. Dehorning caused a marked cortisol increase which was reduced to control concentrations by local anaesthesia for as long as the associated nerve blockade lasted. CONCLUSIONS: The very short-lived adrenaline responses in calves were attributed to dehorning-induced nociceptor input leading to sympathetic stimulation of the adrenal medulla. The longer lasting noradrenaline responses in lambs and calves were thought be due to 'wash-out' of noradrenaline from damaged tissue associated with rings and amputation wounds, respectively.  相似文献   

6.
As a result of a marked decline in dry matter intake (DMI) prior to parturition and a slow rate of increase in DMI relative to milk production after parturition, dairy cattle experience a negative energy balance. Changes in nutritional and metabolic status during the periparturient period predispose dairy cattle to develop hepatic lipidosis and ketosis. The metabolic profile during early lactation includes low concentrations of serum insulin, plasma glucose, and liver glycogen and high concentrations of serum glucagon, adrenaline, growth hormone, plasma β-hydroxybutyrate and non-esterified fatty acids, and liver triglyceride. Moreover, during late gestation and early lactation, flow of nutrients to fetus and mammary tissues are accorded a high degree of metabolic priority. This priority coincides with lowered responsiveness and sensitivity of extrahepatic tissues to insulin, which presumably plays a key role in development of hepatic lipidosis and ketosis. Hepatic lipidosis and ketosis compromise production, immune function, and fertility. Cows with hepatic lipidosis and ketosis have low tissue responsiveness to insulin owing to ketoacidosis. Insulin has numerous roles in metabolism of carbohydrates, lipids and proteins. Insulin is an anabolic hormone and acts to preserve nutrients as well as being a potent feed intake regulator. In addition to the major replacement therapy to alleviate severity of negative energy balance, administration of insulin with concomitant delivery of dextrose increases efficiency of treatment for hepatic lipidosis and ketosis. However, data on use of insulin to prevent these lipid-related metabolic disorders are limited and it should be investigated.  相似文献   

7.
To determine the effects of exercise, high heat and humidity and acclimation on plasma adrenaline, noradrenaline, beta-endorphin and cortisol concentrations, five horses performed a competition exercise test (CET; designed to simulate the speed and endurance test of a three-day event) in cool dry (CD) (20 degrees C/40% RH) and hot humid (30 degrees C/80% RH) conditions before (pre-acclimation) and after (post-acclimation) a 15 day period of humid heat acclimation. Plasma adrenaline and noradrenaline concentrations pre-acclimation were significantly increased compared with exercise in the CD trial at the end of Phases C (P<0.05) and D (P<0.05 and P<0.01, respectively) and at 2 min recovery (P<0.01), with adrenaline concentrations still elevated after 5 min of recovery (P<0.001). Plasma beta-endorphin concentrations were increased at the end of Phases C (P<0.05) and X (P<0.01) and at 5 and 30 min recovery (P<0.05) in the pre-acclimation session. Plasma cortisol concentrations were elevated after the initial warm up period pre-acclimation (P<0.01) and at the end of Phase C (P<0.05), compared with the CD trial. A 15 day period of acclimation significantly increased plasma adrenaline concentrations at 2 min recovery (P<0.001) and plasma cortisol concentration at the end of Phase B (P<0.01) compared with pre-acclimation. Acclimation did not significantly influence noradrenaline or beta-endorphin responses to exercise, although there was a trend for plasma beta-endorphin to be lower at the end of Phases C and X and after 30 min recovery compared with pre-acclimation. Plasma adrenaline, noradrenaline, beta-endorphin and cortisol concentrations were increased by exercise in cool dry conditions and were further increased by the same exercise in hot humid conditions. Exercise responses post-acclimation suggest that adrenaline and noradrenaline may play a role in the adaptation of horses to thermal stress and that changes in plasma beta-endorphin concentrations could be used as a sensitive indicator of thermal tolerance before and after acclimation. The use of plasma cortisol as a specific indicator of heat stress and thermal tolerance before or after acclimation in exercising horses appears limited.  相似文献   

8.
The adrenal responses in calves submitted to simulated transport on three occasions for 30 min were evaluated. Plasma adrenaline, cortisol and NEFA increased significantly during simulated transport but became less marked in successive trials. Haematological stress-related parameters (Hb, PCV) increased to the same extent on repeated exposure to simulated transport. Plasma noradrenaline, glucose and cholesterol values were unchanged throughout the study.  相似文献   

9.
To study the regulation of leptin secretion in sheep, we infused glucose (0.32 g/h/kg for 12 h) into GH-transgenic animals (n = 8) that have chronically high plasma concentrations of ovine GH and insulin, but low body condition and low plasma leptin concentrations, and compared the responses with those in controls (n = 8). In both groups, the infusion increased plasma concentrations of glucose and insulin within 1 h and maintained high levels throughout the infusion period (P < 0.0001). Compared with controls, GH-transgenics had higher concentrations of insulin, IGF-1, GH (all P < 0.0001) and cortisol (P < 0.05), but lower GH pulse frequency (P < 0.0001). Overall, leptin concentrations were lower in GH-transgenics than in controls (P < 0.01). A postprandial increase in leptin concentrations was observed in both groups, independently of glucose treatment, after which the values remained elevated in animals infused with glucose, but returned to basal levels in those infused with saline, independently of transgene status. In both GH-transgenics and controls, glucose infusion did not affect the concentrations of GH, IGF-1, or cortisol. In conclusion, GH-transgenic and control sheep show similar responses to glucose infusion for leptin and other metabolic hormones, despite differences between them in body condition and basal levels of these hormones. Glucose, insulin, GH, IGF-1 and cortisol are probably not major factors in the acute control of leptin secretion in sheep, although sustained high concentrations of GH and IGF-1 might reduce adipose tissue mass or inhibit leptin gene expression.  相似文献   

10.
The effects of manual blood sampling and remote blood sampling using automatic blood sampling equipment (ABSE) on plasma cortisol and catecholamine concentrations were studied on eight adult female reindeer (Rangifer tarandus tarandus). Contemporary body temperatures and heart rates were also recorded to determine their utility as other possible stress indicators. The animals were blood sampled once every hour with ABSE on 9-10 May and then by manual blood sampling on 13-14 May. Animals were also fitted with equipment to record heart rate and body temperature. Heart rate and body temperature were also recorded continuously without blood sampling on 17-18 May in undisturbed control conditions. Plasma cortisol concentrations were five-to-six fold greater during manual blood sampling compared to sampling with ABSE (F(1,3) = 13.34, P < 0.05). Plasma noradrenaline concentrations were significantly higher (F(1,3) = 22.98, P < 0.05) during manual blood sampling compared to sampling with ABSE, whereas plasma adrenaline concentrations did not differ. Heart rate was higher during manual blood sampling compared to control values. Body temperature was significantly higher during manual sampling compared to values recorded without blood sampling (F(1,4)= 31.65, P < 0.01). In conclusion, plasma cortisol concentration provides an excellent indicator of handling stress in reindeer. The use of ABSE for blood sampling enables measurements of plasma cortisol levels close to basal concentrations that may be used for reference values in studies where indicators of physiological stress are required.  相似文献   

11.
Colostrum feeding and glucocorticoid administration affect glucose metabolism and insulin release in calves. We have tested the hypothesis that dexamethasone as well as colostrum feeding influence insulin-dependent glucose metabolism in neonatal calves using the euglycemic-hyperinsulinemic clamp technique. Newborn calves were fed either colostrum or a milk-based formula (n=14 per group) and in each feeding group, half of the calves were treated with dexamethasone (30 microg/[kg body weight per day]). Preprandial blood samples were taken on days 1, 2, and 4. On day 5, insulin was infused for 3h and plasma glucose concentrations were kept at 5 mmol/L+/-10%. Clamps were combined with [(13)C]-bicarbonate and [6,6-(2)H]-glucose infusions for 5.5h (i.e., from -150 to 180 min, relative to insulin infusion) to determine glucose turnover, glucose appearance rate (Ra), endogenous glucose production (eGP), and gluconeogenesis before and at the end of the clamp. After the clamp liver biopsies were taken to measure mRNA levels of phosphoenolpyruvate carboxykinase (PEPCK) and pyruvate carboxylase (PC). Dexamethasone increased plasma glucose, insulin, and glucagon concentrations in the pre-clamp period thus necessitating a reduction in the rate of glucose infusion to maintain euglycemia during the clamp. Glucose turnover and Ra increased during the clamp and were lower at the end of the clamp in dexamethasone-treated calves. Dexamethasone treatment did not affect basal gluconeogenesis or eGP. At the end of the clamp, dexamethasone reduced eGP and PC mRNA levels, whereas mitochondrial PEPCK mRNA levels increased. In conclusion, insulin increased glucose turnover and dexamethasone impaired insulin-dependent glucose metabolism, and this was independent of different feeding.  相似文献   

12.
Six Welsh gelding ponies were premedicated with 0.03 mg/kg of acepromazine intravenously (i.v.) prior to induction of anaesthesia with midazolam at 0.2 mg/kg and ketamine at 2 mg/kg i.v.. Anaesthesia was maintained for 2 h using 1.2 % halothane concentration in oxygen. Heart rate, electrocardiograph (ECG), arterial blood pressure, respiratory rate, blood gases, temperature, haematocrit, plasma arginine vasopressin (AVP), dynorphin, ß-endorphin, adrenocorticotropic hormone (ACTH), cortisol, dopamine, noradrenaline, adrenaline, glucose and lactate concentrations were measured before and after premedication, immediately after induction, every 20 min during anaesthesia, and at 20 and 120 min after disconnection. Induction was rapid, excitement-free and good muscle relaxation was observed. There were no changes in heart and respiratory rates. Decrease in temperature, hyperoxia and respiratory acidosis developed during anaes-thesia and slight hypotension was observed (minimum value 76 ± 10 mm Hg at 40 mins). No changes were observed in dynorphin, ß-endorphin, ACTH, catecholamines and glucose. Plasma cortisol concentration increased from 220 ± 17 basal to 354 ± 22 nmol/L at 120 min during anaesthesia; plasma AVP concentration increased from 3 ± 1 basal to 346 ± 64 pmol/L at 100 min during anaesthesia and plasma lactate concentration increased from 1.22 ± 0.08 basal to 1.76 ± 0.13 mmol/L at 80 min during anaesthesia. Recovery was rapid and uneventful with ponies taking 46 ± 6 min to stand. When midazolam/ketamine was compared with thiopentone or detomidine/ketamine for induction before halothane anaesthesia using an otherwise similar protocol in the same ponies, it caused slightly more respiratory depression, but less hypotension. Additionally, midazolam reduced the hormonal stress response commonly observed during halothane anaesthesia and appears to have a good potential for use in horses.  相似文献   

13.
The effects of heat exposure and type of diet on the insulin secretory response to glucose and glucose disposal in response to insulin action in female sheep were investigated employing hyperglycemic and euglycemic clamp techniques. Animals were divided into concentrate and roughage diet groups, and were maintained at the same intake levels of metabolizable energy and crude protein in both diets. Each diet group was subjected to either thermoneutral (20°C, 70% RH) or hot (30°C, 70% RH) environment, followed by glucose clamp experiments.

Heat-exposed sheep showed significant increases in respiration rates (P<.001) and rectal temperature (P<.05). Plasma glucose concentrations in the basal conditions were lower (P<.01) in the hot environment than in the thermoneutral environment, but there was no significant difference in basal levels of plasma insulin between the environmental treatments. In the hyperglycemic clamp experiment, mean plasma insulin increments increased (P<.05) during the heat exposure period across diet treatments. The ratio of mean plasma insulin increment to glucose infusion rate tended to be higher (P<.07) in the hot environment than in the thermoneutral environment, but diet treatment did not affect the ratio of mean plasma insulin increment to glucose infusion rate. The euglycemic clamp technique showed that glucose infusion rates remained unchanged among treatments. Insulin secretion response to glucose could be stimulated in the hot environment.  相似文献   


14.
The metabolic mechanisms to circannual changes in body mass of bears have yet to be elucidated. We hypothesized that the Japanese black bear (Ursus thibetanus japonicus) has a metabolic mechanism that efficiently converts carbohydrates into body fat by altering insulin sensitivity during the hyperphagic stage before hibernation. To test this hypothesis, we investigated the changes in blood biochemical values and glucose and insulin responses to intravenous glucose tolerance tests (IVGTT) during the active season (August, early and late November). Four, adult, female bears (5-17 years old) were anesthetized with 6 mg/kg TZ (tiletamine HCl and zolazepam HCl) in combination with 0.1 mg/kg acepromazine maleate. The bears were injected intravenously with glucose (0.5 g/kg of body mass), and blood samples were obtained before, at, and intermittently after glucose injection. The basal triglycerides concentration decreased significantly with increase in body mass from August to November. Basal levels of plasma glucose and serum insulin concentrations were not significantly different among groups. The results of IVGTT demonstrated the increased peripheral insulin sensitivity and glucose tolerance in early November. In contrast, peripheral insulin resistance was indicated by the exaggerated insulin response in late November. Our findings suggest that bears shift their glucose and lipid metabolism from the stage of normal activity to the hyperphagic stage in which they show lipogenic-predominant metabolism and accelerate glucose uptake by increasing the peripheral insulin sensitivity.  相似文献   

15.
Objective: Glucose metabolism is often deranged in septic animals. Bacteremia and sepsis are common in foals and clinical experience suggests that glucose metabolism is abnormal in some of these animals. The purpose of this study was to provide initial estimates of rates of glucose appearance, disappearance, and metabolic clearance rate in septic foals.
Series Summary: Rates of glucose entry, and exit from blood were determined by use of infusion of isotopically labeled glucose in 5 foals with confirmed sepsis. Serum concentrations of glucose, insulin, glucagon, and cortisol were measured concurrent with measurement of rates of glucose turnover. Median glucose turnover rate was 24 μmol/kg/min (range 17–53 μmol/kg/min), and median glucose metabolic clearance rate was 3.2 mL/kg/min (range 1.7–6.7 mL/kg/min). Median concentration of serum immunoreactive insulin was 55 pmol/L (range 36–190 pmol/L), median serum immunoreactive glucagon was 65 pmol/L (range 19–120 pmol/L), and median serum cortisol was 207 nmol/L (range 100–333 nmol/L).
New or unique information provided: These data, although limited in scope and by the lack of data in healthy foals, demonstrate the magnitude and variation in glucose appearance, disappearance, and metabolic clearance rate in septic foals, provide an estimate of rates of glucose utilization in sick foals, and will be useful in guiding future studies of energy metabolism in healthy and ill foals.  相似文献   

16.
German black headed mutton (GBM) ewes are recognized as being highly susceptible to ovine pregnancy toxemia (OPT). The present trial was performed to evaluate whether a breed-dependent gestational diabetes mellitus-like insulin resistance during late pregnancy might be responsible for the high incidence of OPT in the GBM breed. Modified frequently sampled intravenous glucose tolerance tests (300 mg glucose and 0.03 IU insulin per kg of BW) were performed during mid and late pregnancy, the periparturient, and the dry period in polytocous 3.5-yr-old GBM and Finnish Landrace (FL) ewes fed according to their requirements. The corresponding blood samples were analyzed for plasma concentrations of glucose, insulin, nonesterified fatty acids (NEFAs) and β-hydroxybutyrate (β-HB). In addition, the baseline plasma cortisol concentrations were determined during late pregnancy. The BW gain during pregnancy and the rearing success did not differ between the GBM and FL ewes. In both breeds, late pregnancy was associated with decreased basal plasma glucose concentrations and enhanced glucose disposal, as well as elevated baseline β-HB values. Only in the GBM ewes did the plasma NEFA concentrations increase significantly during advancing pregnancy. Moreover, significantly higher baseline plasma NEFA concentrations as well as lower (P < 0.05) basal plasma glucose values were recorded during late pregnancy in the GBM than in the FL ewes. The first-phase insulin secretion, the peripheral insulin sensitivity, and the baseline plasma cortisol values did not differ between both breeds during late pregnancy. It is concluded that increased lipolysis during late pregnancy is a characteristic of the GBM breed. Moreover, elevated plasma NEFA concentrations may contribute to impaired pancreatic insulin response and peripheral insulin resistance in GBM ewes and thus promote OPT.  相似文献   

17.
Four non-lactating cows were offered a maintenance diet of hay wafer and a commercial concentrate. They were housed in a thermoneutral (TN; 20°C) and then a hot (30°C) environment in an artificial climate chamber. Glucose, arginine, butyrate, and insulin were administered through one jugular catheter, and from a catheter on the other side venous blood was collected. The peak increments in plasma insulin after the glucose and butyrate administrations were lower during heat exposure. The response of insulin after arginine injection was smaller in the hot compared with the thermoneutral environment; however, arginine injection resulted in a significantly higher secretion of glucagon in the hot environment. The response area of insulin after the insulin injection was smaller in the hot environment; however, insulin clearance rate was not changed. It is concluded that in non-lactating cows, insulin release is probably lower during heat exposure. With respect to plasma glucose during heat exposure, the lower basal values, lower concentrations after the end of the glucose infusion, and delayed recovery to basal values after the butyrate and insulin administrations observed, may indicate lower gluconeogenesis and glycogenolysis in the hot environment.  相似文献   

18.
Simultaneous application of the euglycemic hyperinsulinemic clamp (EHC) and indirect calorimetry was used to examine heat production, fat, and glucose metabolism in lean and obese adult neutered male and female cats. The results show that in lean insulin-sensitive cats glucose oxidation predominated during fasting, whereas lipid oxidation became more prominent in obese cats. Insulin infusion during the EHC in lean cats and obese male cats led to a large increase in glucose oxidation, glycogenesis, and lipogenesis. It also led to an increase in glucose oxidation and glycogenesis in obese female cats but it was significantly less compared to lean cats and obese males. This indicates that obese females show greater metabolic inflexibility. In obese cats of either gender, insulin caused greater suppression of non-esterified fatty acids compared to lean cats suggesting that obese cats show greater fatty acid clearance than lean cats. The heat production per metabolic size was lower in obese cats than lean cats. This would perpetuate obesity unless food intake is decreased. The higher glucose oxidation rate in obese neutered male cats suggests that they are able to replete their glycogen and lipid stores at a faster rate than females in response to insulin and it implies that they gain weight more rapidly. Further studies are needed to investigate if the different response to insulin of male cats is involved in their higher risk to develop diabetes.  相似文献   

19.
Chronic elevation of glucocorticoid concentrations is detrimental to health. We investigated effects of chronic increase in plasma cortisol concentrations on energy balance and endocrine function in sheep. Because food intake and reproduction are regulated by photoperiod, we performed experiments in January (JAN) and August (AUG), when appetite drive is either high or low, respectively. Ovariectomized ewes were treated (intramuscularly) daily with 0.5 mg Synacthen Depot® (synthetic adrenocorticotropin: ACTH) or saline for 4 wk. Blood samples were taken to measure plasma concentrations of cortisol, luteinising hormone (LH), follicle-stimulating hormone (FSH), growth hormone (GH), leptin, insulin, and glucose. Adrenocorticotropin treatment increased concentrations of cortisol. During JAN, treatment reduced food intake transiently, but increased food intake in AUG. Leptin concentrations were reduced and glucose concentrations were greater in AUG, and insulin concentrations were similar throughout the year. Treatment with ACTH increased leptin concentrations in AUG only, whereas insulin concentrations increased in JAN only. Synacthen treatment increased glucose concentrations, with a greater effect in JAN. Changes in truncal adiposity and ACTH-induced cortisol secretion were positively correlated in JAN and negatively correlated in AUG. Treatment reduced the plasma LH pulse frequency in JAN and AUG, with an effect on pulse amplitude in JAN only. Treatment did not affect plasma GH or FSH concentrations. We conclude that chronically elevated cortisol concentrations can affect food intake, adiposity, and reproductive function. In sheep, effects of chronically elevated cortisol concentrations on energy balance and metabolism depend upon metabolic setpoint, determined by circannual rhythms.  相似文献   

20.
The effects of intravenous urea infusion on glucose turnover, glucose carbon recycling, glucose pool size and glucose clearance were studied in buffaloes kept in either normal ambient temperature or acute heat exposure. Heat stressed animals showed increases in glucose turnover rate, plasma glucose concentration and glucose clearance but decreased glucose carbon recycling. A marked reduction of glucose turnover and glucose clearance associated with increased plasma glucose concentration in heat stressed animals after urea infusion reflects under-utilization of this compound. Mechanisms involved in glucose metabolism during urea infusion in buffaloes are discussed.  相似文献   

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