“Micro”-Insulin Radioimmunoassay: Measurement of the Insulin Response during Glucose Tolerance Tests in Guinea Pigs 1

Abstract

Summary

A method is presented for the radioimmunoassay of insulin levels in small volumes of serum collected by multiple bleedings of guinea pigs. The validity of this technique was evaluated by both parallelism and recovery studies. The assay was utilized to measure the insulin response to a glucose tolerance test in fed, fasted, and fasted + refed groups of animals.

Insulin levels in guinea pigs under basal conditions were 10-fold higher than those reported for other species. A significant decline in both basal blood glucose and insulin levels occurred following a 24-hr fast. Fasted guinea pigs also demonstrated an impairment of glucose tolerance and a delayed insulin peak; both of these abnormalities were reversed by refeeding. These results suggest that although the guinea pig possesses an unusually high blood level of immunoreactive insulin, its insulin and glucose responses to fasting and glucose tolerance tests are similar to those reported for other species.