Endocrinology, Vol 122, 1810-1815, Copyright © 1988 by Endocrine Society

ARTICLES

Effect of withdrawal of somatostatin and growth hormone (GH)-releasing factor on GH release in vitro

J Kraicer, MS Sheppard, J Luke, B Lussier, BC Moor and JS Cowan
Department of Physiology, University of Western Ontario, London, Canada.

The secretion of GH, in vivo, is pulsatile. We have proposed that the timing of the episodic bursts of GH secretion is set by somatostatin (SRIF) withdrawal, while the magnitude of the bursts is set by the amount of GH-releasing factor (GRF) impinging on the somatotrophs, before and during SRIF withdrawal. We have now used an in vitro model of perifused rat pars distalis cells to further examine the interaction between GRF and SRIF on the magnitude of the burst of GH release that follows SRIF withdrawal. We first characterized the GH response, with time, to constant perifusion with GRF. The initial burst, followed by a rapid decrease in GH release induced by constant perifusion is due to a loss of GRF bioactivity in the perifusion medium and not to a decreasing responsiveness of the somatotrophs. This was followed by studies on the interaction between GRF and SRIF. The burst of GH release after cessation of perifusion with SRIF (10(-9) M) plus GRF (10(-10) M) can be blocked by the administration of SRIF during the burst. Also, the magnitude of the burst is proportional to the concentration of GRF preceding the withdrawal of SRIF. It is likely that similar relations apply in vivo, where SRIF withdrawal sets the timing and duration of the episodic burst of GH release, while GRF sets the magnitude.

This article has been cited by other articles:

				M.C. Lacroix, P. Bolifraud, D. Durieux, A. Pauloin, M. Vidaud, and G. Kann Placental Growth Hormone and Lactogen Production by Perifused Ovine Placental Explants: Regulation by Growth Hormone-Releasing Hormone and Glucose Biol Reprod, March 1, 2002; 66(3): 555 - 561. [Abstract] [Full Text] [PDF]

				A. Giustina and J. D. Veldhuis Pathophysiology of the Neuroregulation of Growth Hormone Secretion in Experimental Animals and the Human Endocr. Rev., December 1, 1998; 19(6): 717 - 797. [Abstract] [Full Text]

				F. I. Sharara and L. C. Giudice Role of Gorwth Hormone in Ovarian Physiology and Onest of Puberty Reproductive Sciences, January 1, 1997; 4(1): 2 - 7. [Abstract] [PDF]