Decreased Glucagon Receptors in Diabetic Rat Hepatocytes: EVIDENCE FOR REGULATION OF GLUCAGON RECEPTORS BY HYPERGLUCAGONEMIA

• Text
• PDF

Abstract

The effects of endogenous and exogenous hyperglucagonemia on the specific binding of glucagon to hepatocyte receptors was studied, as was the response of cAMP to glucagon. In streptozotocin diabetic rats, blood glucose and plasma glucagon increased and plasma insulin decreased as compared with controls. Insulin treatment in diabetic rats restored blood glucose and plasma glucagon toward normal and elevated plasma insulin. Specific binding of 125I-glucagon to isolated hepatocytes (106 cells) decreased in diabetic rats (8.17±0.38%) compared to controls (14.05±0.87%) and was restored by insulin treatment (12.25±0.93%). Specific binding of 125I-insulin in controls was 7.30±10.16%; it increased in diabetic rats to 12.50±0.86%, and decreased in diabetic rats after insulin treatment (9.08±0.87%). Scatchard analysis and the competition plots of the data indicate that decreased glucagon binding and increased insulin binding in diabetes were due to change in the number of receptors rather than a change in their affinity. Hepatocyte cAMP response to glucagon (0.25-5.0 ng/ml) was almost abolished in diabetic rats and was restored with insulin treatment.

Authors

Sam J. Bhathena, Nancy R. Voyles, Stewart Smith, Lillian Recant