Insulin release from pancreatic islets: effects of CRF and excess PTH

Insulin secretion may be impaired in chronic renal failure (CRF) and available data suggest that this abnormality may be related to the state of secondary hyperparathyroidism of renal failure. We directly measured insulin release from isolated islets of Langerhans obtained from normal rats, CRF-control and CRF-PTX (parathyroidectomized) rats, and parathyroid hormone (PTH)-treated animals. Both early and total glucose-induced insulin release from islets of CRF-control were markedly and significantly (P less than 0.01) lower than from islets of normal rats. Insulin release from islets of CRF-PTX rats was significantly (P less than 0.01) higher than that from islets of CRF-control rats, and not different from insulin release from islets of normal rats. Forskolin and IBMX, which cause a rise in cAMP, significantly stimulated glucose-induced insulin release from islets of normal, CRF-control and CRF-PTX rats, but the increments from baseline were not significantly different between the three groups. Both early and total insulin release from islets obtained from PTH-treated rats with normal renal function were markedly and significantly (P less than 0.01) lower than values obtained from normal rats. Calcium contents of the pancreas of CRF-control and PTH-treated rats were significantly (P less than 0.01) higher than that in pancreas of normal rats and CRF-PTX animals, and values in the latter two groups of animals were not significantly different. The results show that: 1) CRF impairs insulin release from pancreatic islets; 2) this abnormality is reversed by prior parathyroidectomy; and 3) hyperparathyroidism induced by PTH-treatment in normal rats impairs insulin release from pancreatic islets.(ABSTRACT TRUNCATED AT 250 WORDS)