The effect of placental lactogen (HPL) on glucose-induced insulin release

Abstract

The possible effect of placental lactogen on the process of insulin secretion was investigated in rabbits by examining its action upon glucose-induced insulin secretion. Glucose injection (0.5 g/kg body weight) resulted in a prompt insulin response. When placental lactogen (5 mg/kg body weight) and glucose were injected simultaneously, no significant changes in blood glucose levels were observed as compared to those after glucose alone. Plasma insulin levels 5 min after the combined injection were higher than after glucose alone and the total insulin response appeared to be an additive effect of the two stimulating agents. Insulin secretionin vitro by pieces of pancreatic tissue from rabbits has been studied with and without the addition of glucose and HPL. The dynamics of insulin secretion were examined by sequential exposure of the same pieces of pancreatic tissue. After 60 min of preincubation, 25 µg/ml of partially purified HPL plus glucose significantly increases insulin release. It is suggested that the increase of B-cell secretion during pregnancy could be due, at least in part, to the stimulation of endogenous production of chorionic growth hormone.