Renal clearance, insulin secretion and glucose tolerance in spontaneous diabetes mellitus of dogs.

A standard intravenous glucose tolerance test (IVGTT) and the insulin response to the glucose loads were studied in 14 cases of diabetes mellitus in dogs. In addition, urinary glucose excretion, and clearances of urea, creatinine and phosphate were also determined in these dogs. All diabetic dogs were characterized by glucose intolerance as expressed by an abnormal half-time (T 1/2) or fractional clearance rate (k-value) and were further classified as Types I, II or III diabetes on the basis of their insulin responses. Renal functional impairment was observed in about 60 percent of the cases and was generally mild. There appeared to be no apparent relationship between advanced chronic renal disease and severity of diabetes in dogs.     

Effects of phenylbutazone on glucose tolerance and on secretion of insulin in healthy geldings

The effect of phenylbutazone (4.4 mg/kg of body weight, IV, q 24 h, for 5 days) on glucose tolerance and on secretion of insulin in 6 healthy geldings was determined. Phenylbutazone significantly lowered fasting concentrations of glucose in plasma but did not significantly change the concentration of insulin in serum. There was no significant effect of phenylbutazone on glucose tolerance, on secretion of insulin, or on the area under the insulin/glucose ratio vs time curve in healthy geldings, as determined by paired t test analysis.     

Determination of reference values for glucose tolerance, insulin tolerance, and insulin sensitivity tests in clinically normal cats

OBJECTIVE: To determine reference values and test variability for glucose tolerance tests (GTT), insulin tolerance tests (ITT), and insulin sensitivity tests (IST) in cats. ANIMALS: 32 clinically normal cats. PROCEDURE: GTT, ITT, and IST were performed on consecutive days. Tolerance intervals (ie, reference values) were calculated as means +/- 2.397 SD for plasma glucose and insulin concentrations, half-life of glucose (T1/2 glucose), rate constants for glucose disappearance (Kglucose and Kitt), and insulin sensitivity index (Si). Tests were repeated after 6 weeks in 8 cats to determine test variability. RESULTS: Reference values for T1/2glucose, Kglucose, and fasting plasma glucose and insulin concentrations during GTT were 45 to 74 minutes, 0.93 to 1.54 %/min, 37 to 104 mg/dl, and 2.8 to 20.6 microU/ml, respectively. Mean values did not differ between the 2 tests. Coefficients of variation for T1/2glucose, Kglucose, and fasting plasma glucose and insulin concentrations were 20, 20, 11, and 23%, respectively. Reference values for Kitt were 1.14 to 7.3%/min, and for SI were 0.57 to 10.99 x 10(4) min/microU/ml. Mean values did not differ between the 2 tests performed 6 weeks apart. Coefficients of variation for Kitt and SI were 60 and 47%, respectively. CONCLUSIONS AND CLINICAL RELEVANCE: GTT, ITT, and IST can be performed in cats, using standard protocols. Knowledge of reference values and test variability will enable researchers to better interpret test results for assessment of glucose tolerance, pancreatic beta-cell function, and insulin sensitivity in cats.     

Glucose tolerance and insulin secretion in spontaneously hyperthyroid cats

Glucose tolerance and insulin secretion after administration of a glucose load were determined in 11 clinically normal cats and 15 cats with spontaneous hyperthyroidism. In six hyperthyroid cats, a glucose tolerance test was repeated after treatment with radioactive iodine (131I). All cats had similar baseline glucose concentrations. However, the cats with hyperthyroidism had a significantly decreased glucose clearance, which was worse after treatment. Hyperthyroidism also caused a marked increase in basal and glucose-stimulated insulin secretion, which was not improved with treatment. It is concluded that hyperthyroidism in cats may lead to long-lasting alterations of glucose tolerance and insulin secretion which may not be reversed by treatment.     

Evaluation of glucose tolerance and insulin sensitivity in Ilama crias

OBJECTIVE: To investigate glucose tolerance and insulin sensitivity in llama crias. ANIMALS: 7 llamas (age range, 14 to 30 days). PROCEDURE: On each of 2 sequential days, crias were administered glucose (0.5 g/kg) via rapid i.v. injection. On 1 day (randomly determined for each cria), regular insulin (0.2 U/kg) or 0.9% NaCl solution (0.002 mL/kg) was administered i.v. 15 minutes after glucose administration. Blood samples were collected before (baseline) and at 5, 15, 30, 45, 60, 90, 120, 180, and 240 minutes after glucose administration for determination of plasma glucose and insulin concentrations; fractional turnover rates and plasma half-life of glucose were calculated. The data were compared over time and between days (ie, between glucose treatments with and without insulin administration). RESULTS: A peak plasma glucose concentration of 342 +/- 47 mg/dL was detected at 5 minutes after glucose administration and llamas cleared glucose from plasma within 60 minutes; at 15 minutes, plasma insulin concentration attained a peak value of 33 +/- 13 microU/mL (ie, triple the baseline value). During the 15- to 45-minute interval, fractional turnover rate of glucose was 1.10 +/- 0.24%/min and plasma half-life was 65.7 +/- 13.4 minutes. Insulin significantly increased glucose turnover and resulted in hypoglycemia within 75 minutes of administration. CONCLUSIONS AND CLINICAL RELEVANCE: Healthy immature llamas have glucose tolerance and insulin sensitivity superior to that of adults. However, whether sick crias retain the pancreatic sufficiency and tissue responsiveness that are likely responsible for the rapid glucose clearance in healthy individuals is not known.     

Renal abscess in a dog with transient diabetes mellitus

A nine-year-old, intact female dalmatian with diabetes mellitus and a renal abscess is described. The renal abscess was treated surgically by nephrectomy, and the diabetes mellitus resolved with ovariohysterectomy. Abdominal ultrasound and ultrasound-guided aspiration of the abscess were helpful in establishing a diagnosis. To the authors' knowledge, this is the first report of a renal abscess in a dog with diabetes mellitus.     

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.     

Glucose tolerance and insulin response in diabetes mellitus of dogs

The low dose intravenous glucose tolerance test (IVGTT) and the insulin response to the glucose load were performed in a series of twenty–two diabetic dogs. All diabetic dogs were characterized by glucose intolerance as expressed by an abnormal half time (Tl/2) or fractional turnover rate (k) for glucose clearance. On the basis of the initial insulin level (Io), the insulin peak response (Ip) and the insulinogenic index (I/G), the dogs were classified into three types. Type I dogs were characterized by a low Io, low Ip and low I/G in response to glucose, similar to the juvenile form of diabetes in humans. Type II dogs were characterized by a normal or high Io, but also with a low Ip and a low I/G which are some of the features of the maturity onset form. Type III dogs were characterized by a normal Io and a normal or delayed response to glucose as seen in chemical diabetes. It is suggested that these types represent stages in the natural history of the development of diabetes mellitus in dogs.     

The effect of Suisynchron on the glucose tolerance and the plasma insulin in bitches

Suisynchron, a derivative of bisthio-urea commonly used for oestric synchronisation, was applied to nine female Alsatians over 21 days. All animals received intravenous glucose injections before ten, and 21 days from the beginning of treatment as well as 21, and 84 days after the end of treatment. The glucose-stimulated plasma insulin levels were significantly reduced during Suisynchron treatment and 21 days after the end of treatment. Both glucose tolerance and response of free fatty acids remained unaffected. This phenomenon might be attributable to a stimulated hepatic insulin degradation, to a biguanid-like effect on "peripheral" glucose turnover, or to an inhibited secretion of hormonal insulin antagonists of the anterior lobe of the pituitary gland. However, the long persistence of the Suisynchron action after interruption of treatment, could not be explained by any of these effects.     

Effects of megestrol acetate on glucose tolerance and growth hormone secretion in the cat

Long-term administration of relatively high therapeutic dosages of megestrol acetate to cats produced a progressive deterioration in glucose tolerance, with a significant (P less than 0.05) increase in mean fasting plasma glucose concentrations and decrease in mean plasma glucose clearance rates after six and 12 months of treatment. There appeared to be no relationship, however, between the development of glucose intolerance and circulating growth hormone (GH) concentrations in the cats of this study, since no significant rise in plasma GH concentrations was detected during the 12 month period of megestrol acetate treatment. Administration of megestrol acetate also produced a progressive decrease in both resting plasma cortisol concentrations and cortisol concentrations after ACTH stimulation. Three months after discontinuation of megestrol acetate, the elevated fasting plasma glucose concentrations, decreased glucose clearance rates and subnormal plasma cortisol concentrations all returned to normal pretreatment values, indicating resolution of glucose intolerance and hypoadrenocorticism. The results of this study demonstrate that administration of megestrol acetate to cats can produce a state of moderate to severe glucose intolerance, which is usually reversible after cessation of treatment. Although the exact mechanism of the glucose intolerance and overt diabetes mellitus induced by progestagen treatment of cats remains unclear, it is likely that these alterations in glucose metabolism result primarily from the glucocorticoid activity intrinsic to megestrol acetate.     

Effect of regular walking exercise on glucose tolerance and insulin response to i.v. glucose infusion in growing beef steers

The purpose of the present paper was to investigate the effect of regular walking exercise on glucose tolerance and insulin response to i.v. glucose infusion in growing beef steers. Four crossbred beef steers walked on a treadmill during a 6 week exercise period (1.2 km/h, 1 h/day and 5 days/week). The changes in plasma glucose and insulin levels following glucose infusion were analyzed immediately prior to (bodyweight: 260.4 ± 24.2 kg) and after (295.7 ± 30.1 kg) the exercise period. The basal levels of plasma glucose (86.4 vs. 82.0 mg/dL, P = 0.040) and insulin (24.5 vs. 14.3 μU/mL, P = 0.016) were significantly lower after the exercise period. Further, the increase in the levels of plasma glucose (420.4 vs. 280.8 mg/dL, P < 0.001) and insulin (94.5 vs. 73.1 μU/mL, P = 0.028) following the glucose infusion decreased after the exercise period. The area under the curve of plasma glucose (108.8 vs. 62.9 mg/dL per min, P < 0.001) and insulin (53.6 vs. 29.7 μU/mL per min, P = 0.018) indicated more rapid clearance of exogenous glucose and less insulin secretion for glucose clearance after the exercise period. These results suggest that regular exercise improves glucose tolerance, with lower insulin response to glucose infusion in growing steers, as observed in rodents and humans.     

Pancreatic islet cell carcinoma in a dog treated with streptozotocin.

After surgical removal of the primary tumor and recurrence of hypoglycemia, a dog with metastatic pancreatic islet cell carcinoma was treated with streptozotocin. Nephrotoxicosis resulted after a single administration of streptozotocin.     

Renal and ureteral duplication in a dog.

Duplication of a kidney and ureter in an 18-month-old male English Bulldog was demonstrated radiographically and was confirmed surgically. Urinary tract infection had been a problem for a year. Antimicrobial therapy resolved the clinical signs of urinary infection but did not eliminate bacteriuria.     

Effects of porcine growth hormone on glucose metabolism of pigs: II. Glucose tolerance, peripheral tissue insulin sensitivity and glucose kinetics

This study was conducted to determine whether the increase in serum glucose observed in pigs treated chronically with pGH is due to an increase in hepatic glucose output or to an impairment in glucose clearance. Barrows (n = 4 per treatment) were treated with pituitary derived pGH (ppGH), recombinant pGH analog (rpGH) or vehicle. Pigs were treated for 28 d by daily i.m. injections. Insulin tolerance and glucose tolerance tests (GTT) were performed on d 19 and 21, respectively, following treatment with pGH. Glucose turnover was quantified on d 28 using [6-3H]glucose. Chronically treating pigs with pGH resulted in a significant decrease (26%; P less than .05) in glucose clearance, as determined by the GTT. Glucose clearance was affected similarly by ppGH and rpGH. Intra-arterial glucose infusion markedly increased plasma insulin concentration in pGH-treated pigs. Peak plasma insulin response was 87% and 58%, respectively, higher (P less than .05) in ppGH- and rpGH-treated than in control pigs. Insulin infusion elicited a marked hypoglycemia in pigs; however, the extent and duration of hypoglycemia were significantly less in pGH-treated pigs (ppGH or rpGH). Glucose production rates were 23% higher (P = .085) in ppGH-treated than in control pigs. These results establish that the hyperglycemia induced by pGH is the result of an increase in hepatic glucose output and a concurrent impairment in glucose clearance.