The Effect of Glucose and Free Fatty Acids on Growth Hormone (GH)-Releasing Factor-Mediated GH Secretion in Rats*

Abstract

We have examined the effect of glucose and FFA on GH-releasing factor (GHRF)-mediated GH secretion in rats under pentobarbital anesthesia. Hyperglycemia did not affect GH secretion induced by administration of 20, 100, and 200 ng GHRF/100 g body weight. In contrast, GH response to 50 ng GHRF/100 g body weight in lipid-heparin treated rats, which showed high plasma FFA levels, was significantly suppressed compared with the control group (plasma peak GH: control, 1526 .+-. 263 ng/ml; lipid-heparin group, 377 .+-. 69 ng/ml P < 0.05, mean .+-. SEM). This suppressive effect of FFA on GH secretion was abolished by pretreatment with antisomatostatin serum (ASS) (GH level at 4 min after GHRF administration: ASS-saline group, 1606 .+-. 210 ng/ml; ASS-lipid-heparin group, 1531 .+-. 174 ng/ml; mean .+-. SEM). These results suggest that hyperglycemia does not change the GH response to GHRF and that elevation of plasma FFA suppresses GHRF-induced GH secretion by the stimulation of somatostatin secretion in rats.