Comparative effects of proligestone and megestrol acetate on basal plasma glucose concentrations and cortisol responses to exogenous adrenocorticotrophic hormone in cats

Cats were given megestrol acetate (MA, 5 mg once daily for 14 days), subcutaneous proligestone (PRG, 100 mg on two occasions one week apart) or subcutaneous saline (1 ml as for PRG). In cats given saline (n = 6) basal cortical concentrations, cortisol concentrations after adrenocorticotrophic hormone (ACTH) administration and fasting blood glucose concentrations did not change significantly during the following seven weeks. Cats given MA (n = 7) developed suppression of basal and ACTH-stimulated cortisol concentrations and fasting hyperglycaemia during treatment. Effects on cortisol persisted for two weeks after MA dosage ceased. In cats given PRG (n = 7), basal cortisol concentrations were reduced overall, but only three cats had persistently suppressed post-ACTH cortisol concentrations. Adrenal suppression continued for 14 weeks in one of these and for at least 22 weeks in two cats. Fasting blood glucose concentrations were unchanged in PRG-treated cats.     

Plasma cortisol responses to three cortico-trophic preparations in normal dogs

Objective To compare cortisol responses to three corticotrophic preparations in normal dogs.
Animals Eight clinically normal dogs (four intact males, four intact females) of medium size.
Procedures Each dog received four treatments on four separate occasions in a duplicated Latin square pattern. Treatments were two adrenocorticotrophin (ACTH) preparations given intramuscularly at 2.2 U/kg, one of the ACTH preparations given intramuscularly at 1 U/kg and a synthetic polypeptide with ACTH-like activity (tetracosactrin, cosyntropin) given intravenously at 5 μg/kg. Plasma samples were taken for cortisol assay before and at 0.5, 1, 2 and 4 h after treatment.
Results Plasma cortisol concentrations were similar with the two ACTH preparations and at both dose rates. Tetracosactrin produced smaller mean peak cortisol concentrations, which tended to occur earlier than with ACTH, and smaller values for the area under the curve of plasma cortisol concentration from zero time to 4 h.
Conclusion The findings suggest that canine adrenal function can be tested adequately by giving ACTH intramuscularly at 1 U/kg and measuring plasma cortisol in samples taken at 0 and 2 h, or by giving tetracosactrin intravenously at 5 μg/kg and determining cortisol concentration at 0 and 1 h.     

Plasma progesterone concentration in beef heifers receiving exogenous glucose, insulin, or bovine somatotropin

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.     

Effects of exogenous insulin on glucose tolerance in alpacas

OBJECTIVE: To evaluate the effects of exogenous insulin on clearance of exogenous glucose in alpacas. ANIMALS: 7 adult castrated male alpacas. PROCEDURE: Prior to each of 2 trials, food was withheld for 8 hours. Glucose (0.5 g/kg of body weight) was then administered by rapid IV infusion. During 1 of the trials, regular insulin (0.2 U/kg, IV) was also administered 15 minutes later. Blood was collected immediately before (0 minutes) and 15, 20, 25, 30, 45, 60, 90, 120, 180, and 240 minutes after glucose administration. Plasma concentrations of glucose and lactate were determined, and glucose fractional turnover rate and plasma half-life were calculated. RESULTS: Insulin treatment caused a significant increase in fractional turnover rate of glucose and plasma lactate concentration. Plasma glucose concentrations were less in insulin-treated alpacas from 30 minutes after glucose administration (15 minutes after insulin administration) until the conclusion of each trial, compared with nontreated alpacas. In addition, plasma glucose concentration in insulin-treated alpacas returned to baseline values 1 hour sooner than in the nontreated group. CONCLUSIONS AND CLINICAL RELEVANCE: Glucose uptake in alpacas improves after insulin treatment, suggesting that administration of exogenous insulin will increase the therapeutic and decrease the pathologic effects of exogenous glucose administered to hypoglycemic alpacas. However, alpacas and other New World camelids should be monitored carefully during treatment with glucose or insulin, because these species appear to be partially insulin resistant.     

Maturation of insulin and glucose responses to normal feeding in foals

SUMMARY Postprandial insulin and glucose concentrations were measured in 3 Arabian and 3 Thoroughbred foals at 1 day, 1 week, 1 month and 3 months of age. Prefeeding serum Insulin concentrations were similar in foals at 1 day (25.9 ± 5.1 pmol/L), 1 week (32.4 ± 5.8 pmol/L), and 1 month (38.2 + 7.9 pmol/L), but had Increased significantly to 131.0 ± 20.2 pmol/L at 3 months of age (P < 0.05). There was significantly increased serum Insulin secretion after a feed In foals at 3 months of age (P < 0.05) when compared with that at younger ages. Prefeeding serum glucose concentrations ranged from 6.0 ± 0.7 mmol/L at 1 day, to 5.9 ± 0.9 mmol/L at 1 week, 4.9 ± 1.7 mmol/L at 1 month, and 4.4 ± 1.5 mmol/L at 3 months of age. There were lower postprandial glucose concentrations with advancing age. It appeared that there was a period of maturation in pancreatic β-cell function after birth in foals, which reached adult levels by 3 months of age.     

Plasma cortisol response to exogenous ACTH in 22 dogs with hyperadrenocorticism caused by adrenocortical neoplasia

The plasma cortisol response to exogenous ACTH (ACTH stimulation test) was evaluated in 22 dogs with hyperadrenocorticism caused by adrenocortical neoplasia. The mean basal cortisol concentration (6.3 microgram/dl) was high, but 7 dogs had basal cortisol concentrations that were within normal range. Administration of exogenous ACTH increased the plasma cortisol concentrations in each dog. Normal post-ACTH cortisol concentrations were found in 9 (41%) of the 22 dogs; 13 (59%) had an exaggerated increase in cortisol concentrations after ACTH administration. In 9 of 13 dogs with carcinoma and in 4 of 9 with adenoma, the cortisol response was exaggerated. The mean post-ACTH cortisol concentration in the dogs with carcinoma was approximately 4 times that of the dogs with adenoma; the 7 dogs with the highest concentrations had carcinoma. Repeat studies were performed in 6 dogs 2 to 8 weeks after initial testing. In 5 of the 6 dogs, repeat testing yielded data of similar diagnostic significance. One dog, however, had an abnormally high post-ACTH cortisol concentration at initial evaluation, but had only a minimal response to ACTH administration, with a normal post-ACTH cortisol concentration, at time of resting. Although ACTH stimulation testing is useful in diagnosing hyperadrenocorticism, it can not reliably separate dogs with hyperfunction adrenocortical tumors from clinically normal dogs or from dogs with pituitary-dependent hyperadrenocorticism (bilateral adrenocortical hyperplasia).     

Plasma cortisol in the horse, diurnal rhythm and effects of exogenous ACTH.

Peripheral blood plasma Cortisol concentration and its diurnal variation was measured in 4 horses. Mean concentration of Cortisol during 24 hrs. was 42 ng/ml (s ± 20 ng/ml). Peak values occurred at 6 a.m. and the lowest values were observed at about 6 p.m. (mean 65 ng/ml and 20 ng/ml, respectively).Long-acting ACTH at a dose of 150 i.u. was given by intramuscular injection to the 4 horses. Peak Cortisol concentrations markedly exceeding the prestimulation level were obtained between 2 and 4 hrs. after injection. During the immediate 24 hrs. after these peaks, the mean Cortisol level was markedly lower and the cyclic variation out of phase with the basal diurnal pattern. After a gradual adjustment during the second postinjection day, no differences could be seen between the 2 patterns on day 3 after injection.     

Plasma cortisol and progesterone responses to low doses of adrenocorticotropic hormone in ovariectmized lactating cows

The objective of this study was to describe the responses of the plasma progesterone and cortisol concentrations in ovariectomized lactating cows to low doses of adrenocorticotropic hormone (ACTH). The estrous cycles in 3 lactating cows were synchronized, and the cows were ovariectomized in the luteal phase. ACTH challenge tests were conducted at doses of 3, 6, 12 and 25 IU. Blood samples were collected at 30 min intervals, and the plasma progesterone and cortisol concentrations were analyzed by EIA. A concomitant rise in plasma progesterone and plasma cortisol was observed in cows treated with 12 IU or higher doses of ACTH. Significant increments in the plasma cortisol concentrations were observed at all doses of ACTH. The means (+/- SE) of the peak plasma progesterone concentrations after the 3, 6, 12 and 25 IU ACTH challenge tests were 0.6 +/- 0.1, 1.3 +/- 0.4, 1.5 +/- 0.3 and 2.4 +/- 0.3 ng/ml, respectively. The means of the peak plasma cortisol concentrations in the 3 cows after the ACTH challenge were 14.0 +/- 1.5, 17.0 +/- 2.5, 23.3 +/- 3.0, and 33.3 +/- 7.0 ng/ml, respectively. The effects of the doses, time after treatment, and their interaction on the plasma progesterone concentrations after the ACTH challenge were significant (P<0.01). Likewise, the effects of the doses, time after treatment, and their interaction on the plasma cortisol concentrations after the ACTH challenge were significant (P<0.01). The mean AUC values for the plasma progesterone and cortisol concentrations after the ACTH treatments were also significantly affected by the dose of ACTH (P<0.01 and P<0.05, respectively). A significantly positive correlation was obtained between the peak plasma progesterone and cortisol concentrations after different doses of ACTH (r=0.7, P<0.05). The results suggest that lactating dairy cows are capable of secreting a significant amount of adrenal progesterone, reaching up to the minimal concentration necessary to cause suppression of estrus in response to 12 IU ACTH (P<0.01). The concomitant plasma cortisol concentration was 23.3 ng/ml.     

Plasma concentrations of cortisol in cows with hypocalcaemia in relation to their responses to treatment with calcium

The mean plasma concentration of cortisol at the time of the first treatment for hypocalcaemia at calving was significantly higher in 17 cows which did not recover, than in 53 cows which recovered. Healthy periparturient cows had significantly lower cortisol levels than cows with hypocalcaemia. There was a negative correlation between plasma cortisol and plasma calcium at the time of the first treatment. After adjustment for differences in plasma calcium there was no significant difference between cortisol concentrations in healthy cows and paretic cows which recovered. Plasma cortisol was positively correlated with both packed cell volume (PCV) and serum creatine kinase (CK). At first treatment cows which did not recover had higher levels of PCV and serum CK than cows which recovered, and the difference between the mean plasma cortisol concentrations of these two groups was related to differences in plasma calcium, PCV and serum CK. Plasma cortisol concentrations remained high in cases of protracted paresis.     

Plasma glucose and insulin responses of Thoroughbred mares fed a meal high in starch and sugar or fat and fiber

Plasma concentrations of glucose and insulin following a meal were compared in twelve Thoroughbred mares fed a pelleted concentrate (PC), a traditional sweet feed high in sugar and starch (SS), or a feed high in fat and fiber (FF). The feeds had similar DE and CP but differed in fat (19, 32, and 166 g/kg DM, respectively), NDF (199, 185, and 369 g/kg DM, respectively) and nonstructural carbohydrates (574, 645, and 247 g/kg, respectively). Mares were randomly assigned to two groups balanced for foaling date and weight. All mares received PC in late gestation; then, after foaling, one group was fed SS and the other FF for trials in early and late lactation. Mares were placed in stalls and deprived of feed overnight. A series of blood samples was collected via a jugular catheter from 0 (baseline) to 390 min after consumption of 1.82 kg of feed. Plasma was analyzed for glucose and insulin. Baseline values, peak values, and areas under curves (AUC) were compared by ANOVA. Baseline values were 74.7 +/- 10.9 mg/dL for glucose and 5.86 +/- 1.80 mIU/L for insulin for all diets and stages. Responses to PC did not differ between the two groups (P > 0.34), indicating the groups were metabolically similar. Peak plasma glucose and insulin concentrations were higher (P < 0.001) in the SS group than in the FF group during early and late lactation. Similarly, glucose and insulin AUC were larger (P < 0.003) in SS than in FF during early and late lactation. These results indicate that metabolic fluctuations are moderated by the replacement of sugar and starch with fat and fiber. This replacement may reduce the risk of certain digestive and metabolic disorders that have been linked to feeding meals of grain-based concentrates to pregnant or lactating mares.     

Plasma endogenous ACTH concentrations and plasma cortisol responses to synthetic ACTH and dexamethasone sodium phosphate in healthy cats

Plasma cortisol responses of 19 healthy cats to synthetic ACTH and dexamethasone sodium phosphate (DSP) were evaluated. After administration of 0.125 mg (n = 5) or 0.25 mg (n = 6) of synthetic ACTH, IM, mean plasma cortisol concentrations increased significantly (P less than 0.05) at 15 minutes, reached a peak at 30 minutes, and decreased progressively to base-line values by 120 minutes. There was no significant difference (P greater than 0.05) between responses resulting from the 2 dosage rates. After administration of 1 mg of DSP/kg of body weight, IV (n = 7), mean plasma cortisol concentrations decreased at postadministration hour (PAH) 1, and were significantly lower than control cortisol concentrations at PAH 4, 6, 8, 10, and 12 (P less than 0.01). Administration of 0.1 mg of DSP/kg, IV (n = 8) or 0.01 mg of DSP/kg, IV (n = 14) induced results that were similar, but less consistent than those after the 1 mg of DSP/kg dosage. Mean plasma cortisol concentrations returned to base-line values by PAH 24. There was not a significant difference between the 3 doses (P greater than 0.05) at most times. Measurement of endogenous ACTH in 16 healthy cats revealed plasma ACTH of less than 20 to 61 pg/ml. Seemingly, administration of synthetic ACTH consistently induced a significant (P less than 0.05) adrenocortical response in healthy cats. On the basis of time-response studies, post-ACTH stimulation cortisol samples should be collected at 30 minutes after ACTH administration to ensure detection of peak adrenocortical response.(ABSTRACT TRUNCATED AT 250 WORDS)     

Assessment of the effects of exogenous long-acting insulin on glucose tolerance in alpacas

OBJECTIVE: To evaluate the effects of long-acting insulin on glucose clearance in alpacas. ANIMALS: 8 adult castrated alpacas. PROCEDURE: On 2 days, food was withheld from alpacas for 8 hours. Alpacas were randomly allocated to receive an SC injection of long-acting insulin (0.4 U/kg) or saline (0.9% NaCI) solution 1 hour before the first of 3 administrations of glucose (at 60, 480, and 1,200 minutes after treatment) on day 1 and the alternate treatment and procedure on day 2. Plasma glucose concentration was determined before and 15, 45, 120, and 240 minutes after each glucose administration, and fractional turnover rates were calculated. The data were compared between alpacas with and without insulin administration and among the 3 glucose administrations for each day. RESULTS: Compared with sham-treated alpacas, insulin-treated alpacas had significantly lower blood glucose concentrations from 180 to 600 minutes after treatment; they also had glucose concentrations significantly below baseline values from 120 to 480 minutes, at which time the mean glucose concentration was in the hypoglycemic range. Also, mean fractional turnover of glucose was significantly higher in insulin-treated alpacas from 105 through 300 minutes. CONCLUSIONS AND CLINICAL RELEVANCE: Compared with known effects of regular insulin in alpacas, the action of long-acting insulin was of slower onset but longer lasting; its administration may induce hypoglycemia, even in alpacas that receive glucose. To maintain the hypoglycemic effect, long-acting insulin may have to be administered more than once daily and blood glucose concentration should be monitored to avoid hypoglycemic complications in alpacas.     

Relationship between plasma insulin and triglyceride concentrations in hypertriglyceridaemic donkeys

Hyperinsulinaemia is a commonly-observed characteristic of insulin resistance, and a reduction in insulin sensitivity is thought to be either a causative and/or symptomatic feature of equine hyperlipaemia. A positive correlation (r=0·545, P=0·0015) existed between plasma insulin and triglyceride concentrations determined in 31 donkeys with naturally occurring hyperlipidaemia/hyperlipaemia. Greater insulin values tended to occur in the animals with an overweight body score. Inter-animal variation in insulin concentrations, however, prevented the identification of any differences either within hypertriglyceridaemic donkeys (when classified by clinical condition, date of arrival to a sanctuary and eventual outcome after treatment) or between groups of normotriglyceridaemic (n=6) and experimentally fasted hypertriglyceridaemic (n=5) donkeys. Determination of basal plasma insulin concentrations may not provide an accurate assessment of underlying insulin sensitivity. Alternatively, hyperinsulinaemia may be evident only in animals with established insulin resistance.     

Effect of dietary vitamin E on cortisol and glucose responses to handling stress in juvenile beluga Huso huso

An 8-week feeding experiment was conducted to investigate the effect of dietary vitamin E on the physiological response to handling stress in juvenile beluga Huso huso. Fish were fed six experimental diets supplemented with 0, 25, 50,100, 200, or 400 mg Dl-all-rac-alpha-tocopherol acetate/kg diet. At the end of the experiment, the fish in each tank were subjected to acute handling and air exposure stress. Cortisol and glucose were measured as the primary hormonal and secondary metabolic responses to the stressors, both before and 3 h after application of the stressors. The growth parameters and feed utilization rates were significantly lower in fish fed the diet not supplemented with vitamin E than in fish fed diets supplemented with vitamin E. Cortisol concentration was not affected by dietary treatment but glucose concentration was. Fish fed vitamin E at 0, 25, 100, and 400 mg/kg diet had higher concentrations of glucose than those fed vitamin E at 50 and 200 mg/kg. However, fish fed diets with 50 and 200 mg/kg exhibited higher growth rates. These results indicate that dietary vitamin E has some effect on plasma glucose but no effect on plasma cortisol. In general, when the stressors were applied to belugas, the glucose and cortisol responses were relatively low. This may be due to higher resistance and lower physiological responses to these types of stressors by this species or by chondrosteans in general.