Regulation of insulin secretion in the ovine foetus in utero. Effects of sodium valerate on secretion and of adrenocorticotrophin-induced premature parturition on the insulin secretory response to glucose.

Abstract

SUMMARY Intravenous infusions of glucose into lambs in utero (130–150 days) and after birth, confirmed the marked post-natal increase in the magnitude of the response of plasma insulin to glucose. These studies also suggest that insulin secretion in foetal lambs is stimulated by glucose at lower plasma concentrations than in lambs after birth. The short-chain fatty acid, valeric acid, given as the sodium salt, caused a very rapid increase in the plasma insulin level of foetal lambs, when given either by intravenous injection or infusion. When birth was induced after only 135 days of gestation by i.v. infusion of a synthetic adrenocorticotrophin preparation (Synacthen) into foetal lambs there was also a prematurely induced maturation of the insulin secretory response to glucose. In these prematurely born lambs the insulin secretory response to i.v. glucose infusion was similar to that of normal lambs after birth and differed greatly from that of normal foetuses of similar age. The results indicate that maturation of the insulin secretory mechanism in the lamb is associated with parturition and suggest that these changes may be consequences of the increasing corticosteroid secretion in the foetus during the last few days of gestation.