Prednisone was administered orally for 4 weeks at a dosage of 1.1 mg/kg of body weight/d, in divided dose every 12 hours, to a group of healthy adult dogs (n = 12). Intravenous glucose tolerance testing was performed before and after the 28-day regimen in each dog, as well as in dogs of a control group (n = 6). Glucose metabolism was evaluated by measurement of preprandial plasma insulin and glucose concentrations, total insulin secretion, and fractional clearance of glucose. Mean preprandial plasma insulin and glucose concentrations were not increased after the 4-week regimen of prednisone. Total insulin secretion in response to an IV administered glucose load was not increased in treated dogs, compared with pretreatment values or with values for control dogs. The fractional clearance of glucose was also not altered in dogs given prednisone. Results indicate that anti-inflammatory doses of prednisone, given orally for 4 weeks, probably do not alter insulin sensitivity or glucose tolerance in clinically normal dogs.

After IV administration of 0.5 mg of glucagon/cat, glucose tolerance and insulin secretory response were evaluated in 10 lean cats, 10 obese cats, and 30 cats with diabetes mellitus. Blood samples for glucose and insulin determinations were collected immediately before and at 5, 10, 15, 30, 45, and 60 minutes after IV administration of glucagon. Baseline serum insulin concentration and insulin secretory response were used to classify diabetes mellitus in the 30 cats as type I or type II. Mean (+/- SEM) baseline and 30-minute serum glucose concentrations in obese cats were significantly (P < 0.05) decreased, compared with values in lean cats, but were similar at all other blood sample collection times. Serum glucose concentration in diabetic cats was significantly (P < 0.05) greater than values in obese and lean cats at all blood sample collection times. Two statistically different insulin responses to IV administration of glucagon were seen in diabetic cats. Of the 30 diabetic cats, 23 had minimal insulin secretory response after glucagon administration (ie, serum insulin concentration was at or below sensitivity of the insulin assay). Seven diabetic cats had baseline serum insulin concentration similar to that of obese cats and significantly (P < 0.05) greater than that of lean cats and of the other 23 diabetic cats. In these 7 diabetic cats, serum insulin concentration increased after glucagon administration. Total insulin secretion was not significantly different between these 7 diabetic cats and the lean and obese cats, and was significantly (P < 0.05) greater than total insulin secretion in the other 23 diabetic cats. Results support existence of type-I and type-II diabetes mellitus in cats.