ACUTE STRESS-INDUCED HYPERINSULINEMIA IN THE PERTUSSIS TOXIN-TREATED RAT - POSSIBLE ROLE OF HUMORAL BETA-CELL-TROPIC FACTORS

The present study was undertaken to determine if acute stress induced by exposure to ether resulted in the presence of beta-cell-tropic fact ors in rat plasma and if this insulinotropic activity was increased by pertussis toxin. Rats pretreated with pertussis toxin (5 mu g/kg, 5 d ays previously) showed marked hyperinsulinemia, but only after exposur e to ether before blood sampling. This hyperinsulinemia was not modifi ed by adrenal demedullation. Effects on insulin secretion were assesse d by incubation of plasma (diluted with Krebs buffer) with collagenase -isolated rat pancreatic islets. When blood was collected by decapitat ion from normal rats, the subsequently prepared plasma (12.5% to 50%) profoundly inhibited insulin release from rat isolated islets. This in hibition was probably mediated by catecholamines, since it was not see n with plasma from adrenal-demedullated rats and was prevented by alph a(2)-adrenoceptor-blocking drugs. Plasma from adrenal-demedullated, pe rtussis toxin-treated rats stimulated insulin secretion (by 60%) when the donor rats had been exposed to ether before blood sampling. It is suggested that stress may result in the presence of circulating beta-c ell-tropic factors, which may contribute to the acute stress-induced h yperinsulinemia seen in pertussis toxin-treated animals. Copyright (C) 1994 by W.B. Saunders Company