Changes in the islets of langerhans in the obese Zucker rat.

Pancreatic islet tissue from lean and obese Zucker rats was investigated with histologic and immunocytochemical techniques, and the changes in cytologic composition were correlated with levels of serum glucose, lipids, and insulin. The insular changes in obese rats progressed in severity with increasing age. Changes consisted of pronounced insulin cell hyperplasia, disarrangement of islet architecture, and disappearance (degranulation?) of a new islet cell type, the pancreatic polypeptide cell. High levels of free fatty acids, triglyceride, and insulin were detected in serum of obese rats. Upon diet restriction, these parameters decreased and islet morphology became normalized. When obese Zucker rats were treated with streptozotocin, high levels of serum free fatty acids and triglycerides remained but there was a great reduction in serum insulin levels to near normal levels. Pancreatic polypeptide cells werenot found in the islets. It is suggested that high free fatty acid and triglyceride levels in obese rats may be related to the inability to demonstrate pancreatic polypeptide cells in the islets of 100- to 300-day-old obese Zucker rats.