Restoration by Adenosine and Theophylline of Glucose-induced Insulin Responsiveness in Newborn Rats

Abstract

The insulin responsiveness of the isolated islets to various agents was studied in one-day-old and adult rats in an in vitro incubation system.

The responsiveness to 16.7 mM glucose and 16.7 mM glucose plus 1.3 mM theophylline was lower in younger age rats, while that to 16.7 mM glucose plus 10.0 mM adenosine was not different between both age groups. On the other hand, the relative ATP concentration, which implied the ratio of ATP content per unit weight of islet induced by various agents to that by 3.3 mM glucose, did not increase so much in one-day-old rat islets as in adult ones when they were incubated in 16.7 mM glucose and in 16.7 mM glucose plus 1.3 mM theophylline, while it showed no significant difference between both groups when they were incubated in 16.7 mM glucose plus 10.0 mM adenosine.

These observations suggest that rat islets might respond to not only the increase of cyclic AMP but also that of relative ATP concentration, releasing insulin, and that newborn islets might not be equipped with the mature adenyl cyclase-cyclic AMP system as contrasted to adult ones.

Key words

Insulin Release - ATP Concentration - Isolated Islets - Theophylline - Adenosine - Newborn Rats - in Vitro