Endocrinology, Vol 99, 678-683, Copyright © 1976 by Endocrine Society

ARTICLES

Influence of synthetic somatostatin upon growth hormone release from perifused rat pituitaries

ME Stachura

Basal release of pre-labeled, stored tritiated rat growth hormone ([3H]rGH) from perfused rat pituitary explants is a constant fraction of pituitary [LH]rGH content. Synthetic somatostatin (SRIF) inhibits the release of pre-labeled, stored [3H]rGH in a dose-dependent fashion. Prolonged exposure to SRIF results in an immediate and continuous inhibition of [3H]rGH release. In the in vitro perifusion system, the maximal inhibition, which is achieved with 25 nM SRIF, results in a rate of [3H]rGH release which is 30 to 40 per cent of basal release. Pulses of SRIF produce inhibition of [3H]rGH release followed by rebound release after withdrawal of SRIF. When the time of exposure to SRIF is held constant, both the SRIF-induced inhibition and the rebound release of [3H]rGH are dose-dependent. A similar progressive response is seen when a constant SRIF concentration is pulsed for variable periods of time. There is no net inhibition of [3H]rGH release by pulses of SRIF.

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				M. Lumpkin, A Gegro-Vilar, and S. McCann Paradoxical elevation of growth hormone by intraventricular somatostatin: possible ultrashort-loop feedback Science, March 6, 1981; 211(4486): 1072 - 1074. [Abstract] [PDF]