Alterations in Glucagon Secretion in Obese Rats with Hypothalamic Lesions

Summary

Studies were made on changes in the level of plasma immunoreactive glucagon (IRG) in rats with lesions of the ventromedial hypothalamic area.

In the rats with hypothalamic lesions (HTL) the basal level of plasma immunoreactive insulin was higher and its responses to intravenous injection of glucose and to intraperitoneal administration of arginine were significantly greater than those in control rats. The basal plasma IRG concentration was lower and its changes in response to 24 hr starvation or the arginine load were significantly less in rats with HTL than in controls at 1 and 10 weeks after the operation. Similar results were also obtained in the rats pair-fed for 4 weeks after the operation. A significant negative correlation was observed between the basal plasma IRG level and body weight or Lee's index in these rats.

These data suggest that disturbance of the autonomic nervous system due to destruction of the hypothalamus, reduced secretion of pituitary hormones, increased insulin secretion and defect in humoral factors of the hypothalamus may be responsible for the decrease in plasma IRG levels observed in rats with HTL. It also seems likely that reduced glucagon secretion contributes at least in one part to the development of hypothalamic obesity.

Key-Words

Hypothalamic Lesions - Obese Rats - Glucagon - Insulin - Blood Glucose - Fasting - Glucose Tolerance - Arginine Load