Diabetes in pregnancy: islet cell proliferation in the fetal rat pancreas

Since it has not been possible to reproduce, in the rat, the hyperplasia of the islets of Langerhans observed in the fetus in human diabetic pregnancy, the rate of proliferation of the endocrine pancreas of fetuses of manifest diabetic rats has been studied. Rats were rendered diabetic by streptozotocin injections before mating. At days 20 or 22 of gestation the pregnant rats were injected with colchicine and sacrificed at 1-h intervals. The mitotic indices of the fetal endocrine pancreas were determined and plotted against the time after colchicine injection. The production of new cells (i.e. the cell birth rate) was estimated from the slopes of the regression lines. On both days 20 and 22 of gestation, the cell birth rates of the endocrine pancreas of the fetuses of manifest diabetic mothers were only one-third of the control values obtained in normal, age-matched fetal pancreas (daily cell birth rate = 10%). This finding corresponds to the previous observation of a low B cell mass in the offspring of diabetic rats. The results indicate that the growth and development of the fetal endocrine pancreas is retarded in manifest diabetic pregnancy in the rat.