Beta-adrenergic stimulation of growth hormone (GH) release in vivo, and subsequent inhibition of GH-releasing factor-induced GH secretion

Abstract

In vivo and in vitro studies of beta-adrenergic influences on GH secretion have produced apparently conflicting data in which the in vivo effect seems to be inhibitory and the in vitro effect to be stimulatory. The present studies were designed to observe the in vivo effect of isoproterenol (ISO), a beta-adrenergic agonist, on 1) GH release during a brief interval after intraatrial infusion, and 2) GH release in response to GRF infused 10 min after ISO. ISO was found to stimulate GH release in both intact and hypothalamus-lesioned animals within 2 min after infusion, but GH returned to control levels within 10 min. ISO also profoundly inhibited the release of GH in response to GRF. Pretreatment of animals with somatostatin (SRIF) antiserum prevented the inhibitory action of ISO on GRF-induced GH release. No change in peripheral levels of SRIF was detected. Also, there was no suppression of GRF-induced GH release by ISO when the treatments were applied in vitro to dispersed perifused pituitary cells. These data show that beta-adrenergic systems can stimulate a rapid but brief release of GH in vivo, and that the subsequent inhibitory action on GRF-induced GH release might be by means of SRIF release.