POSTNATAL SEQUENTIAL-CHANGES IN ISLET MORPHOLOGY AND INSULIN-SECRETION OF NORMAL HAMSTERS

We have studied the postnatal development of the endocrine pancreas fr om normal female Syrian golden hamsters 1.8, and 24 weeks of age. The observations were made by ca, analysis Of insulin secretion in respons e to glucose using isolated pancreatic islets and (b) identification a nd quantitation of insulin-, glucagon-, somatostatin-, and pancreatic polypeptide-secreting cells. Glucose-induced insulin secretion showed typical dose-response curves. However, whereas in 24-week-old animals maximal secretion was already present with 8 mM glucose, in younger ha msters such a response was attained only with 20 mM glucose. The volum e density of the endocrine pancreas and the number of islets were incr eased in 1-week-old hamsters compared to the older animals. The islet volume average in 8-week-old hamsters was almost three times higher th an that measured in 1-week-old animals. However, the proportion and si ze of each cell type in the islets did not present significant differe nces among the groups studied. Our results show that, in hamsters, the endocrine pancreas reaches the adult general characteristics late aft er birth. Furthermore, the definite morphological pattern is attained far earlier than the secretory response. These observations provide ba sic information for further studies regarding the mechanisms and facto rs that control both the growth and the differentiation of endocrine c ell populations as well as glucose-induced insulin secretion in a simp le experimental model.