Effect of glucocorticoids on insulin sensitivity in newborn dogs

A 3-day treatment with 4 mg/kg Betnesol in anesthetized mongrel pups, 4-55 days of age effectively raised fasting plasma glucose concentration by 23 +/- 2.9%, which was higher than that observed in adult dogs similarly treated. Possibly this was due to the lack of effectiveness of insulin in the pups which is normally produced in response to hyperglycemia. The relative lack of effectiveness of insulin induced hypoglycemia in stimulating hepatic glucose production in the newborn pups was further demonstrated by the fact that insulin administration produced a hypoglycemia which lasted much longer than in adult dogs. On the other hand Betnesol treatment was found to be effective in restoring normoglycemia following administration of insulin in these pups presumably due to its gluconeogenic effect through the liver. In general this investigation points towards the lack of development of appropriate feedback mechanisms for glucose homeostasis in the newborn pups, and that it takes a period of about 3-4 weeks after birth to develop such mechanisms.