Insulin Secretion in Mammosomatotropic Tumor-bearing and Pregnant Rats: A Role for Lactogens Free

The experiments reported here investigate the effects of two conditions of elevated lactogen activity on the threshold of glucose stimulation of insulin secretion and suprathreshold, glucose-stimulated insulin secretion in the isolated, perfused rat pancreas. In both the tumor-bearing animals and pregnant animals, the glucose threshold for insulin release was markedly reduced and the suprathreshold insulin release was elevated over that observed in control pancreata. There was no change on the glucose threshold or extent of release of somatostatin secretion. Altered insulin secretion appears to be readily reversible, since the secretion profile from postlactating animals was not different from the controls. The possible mechanistic role of lactogens is discussed.