Reduction of the beta-cell component of pancreatic islets in spontaneously hypertensive rats.

A morphometric study of the pancreatic islets in young spontaneously hypertensive rats (SHR, Okamoto and Aoki Wistar strain) and in normotensive Wistar rats (NWR) of the same age revealed that the SHR (in prehypertensive and in early hypertensive stages) had a significantly smaller mass of islet tissue and that the number of islets in the SHR was reduced by half. The ratio between the total masses of the pancreatic islets for the NWR and the SHR at the prehypertensive and early hypertensive stages was found to be: 1:0.53:0.61, respectively. The mass of the islet tissue in the SHR was reduced at the expense of the beta-cell component of the islets. No morphologic differences were found in the acinous tissue, and the pancreas and body weights were the same in both experimental groups. The glucose tolerance test revealed reduced glucose utilization in the SHR, which may be due to a relative insufficiency of the insulin secretion by the islets upon rapid (i.v.) glucose lodaing. Reduced plasma insulin response to i.v. glucose loading and a reduced rate of insulin utilization were found in the SHR as compared with the NWR. The poor development of the beta-cell tissue may be attributed either to the specific effect of the enhanced catecholamine excretion or to a low insulin requirement of the cell tissue membranes (insulin targets) as a consequence of the membrane ion transport alteration in spontaneous hypertension.