Metabolic adaptation to pregnancy shown by increased biosynthesis of insulin in islets of Langerhans isolated from pregnant rats

Abstract

MANY reports have indicated that insulin secretion is increased in pregnant women1,2 although blood sugar levels may be unchanged, indicating an increased demand for insulin in human pregnancy. Similar findings have been reported for the effects of pregnancy on insulin secretion in pregnant rats3,4 which begin to respond with a significantly increased insulin secretion at a lower glucose level than those found in the normal female5. In addition, the secretory response is considerably greater in islets of Langerhans from pregnant than in normal rats, indicating an overall increased sensitisation of the islets from pregnant rats to the effects of glucose5. Glucose has a major role in the metabolism of the mammalian β cell, in that at physiological concentrations it is capable of stimulating both insulin secretion and biosynthesis6,7. It is possible that increased insulin biosynthesis is necessary to support the increased secretory response to glucose in pregnancy, if the content of β cell insulin is to be maintained. We have therefore investigated whether the alterations in insulin secretion observed in vivo during pregnancy are paralleled by an enhanced insulin biosynthesis in isolated islets from pregnant rats, after exposure to increasing concentrations of glucose.