Interaction between somatostatin and TRH on growth hormone secretion in perifused human growth hormone tumor cells

The interaction between somatostatin (SRIF) and thyrotropin-releasing hormone (TRH) on growth hormone (GH) release has been studied on dispersed somatotrophic tumor cells obtained from 7 acromegalic patients. TRH increased GH secretion in 4 cases and SRIF decreased GH secretion in 5 cases. When TRH and SRIF were concomitantly perifused, SRIF, when active by itself, prevented and reversed the TRH-induced stimulation of GH release, while TRH never antagonized the inhibitory effect of SRIF. We conclude that, in these adenomatous cells, the physiological inhibitory factor (SRIF) overcomes the nonphysiological stimulatory factor (TRH) in the control of GH secretion.