Endocrinology, Vol 118, 2599-2604, Copyright © 1986 by Endocrine Society

ARTICLES

Gonadotropin-releasing hormone-mediated desensitization of cultured rat anterior pituitary cells can be uncoupled from luteinizing hormone release

HA Jinnah and PM Conn

GnRH stimulates LH release from pituitary gonadotropes. Prolonged exposure of these cells to GnRH results in decreased sensitivity to further stimulation by the releasing hormone both in vivo and in vitro. Chelation of extracellular Ca++ with EGTA blocks GnRH-stimulated LH release but does not prevent subsequent desensitization. Desensitization occurs when cells are preincubated in EGTA containing 10(-7) M GnRH for a variety of times (20 min to 12 h) or when cells are preincubated for 3 h in EGTA with 10(-10), 10(-9), or 10(-8) M GnRH. A GnRH antagonist does not cause desensitization to GnRH and blocks desensitization in response to GnRH in the Ca++-free medium. Preincubation in EGTA containing 10(-7) M GnRH for 3 h did not alter sensitivity of cells to sn 1,2 dioctanoylglycerol (a protein kinase C activator), Ca++ ionophore A23187, or veratridine (an activator of endogenous ion channels). These results suggest that desensitization results from occupancy of the GnRH receptor by an agonist and may be uncoupled from LH release.

This article has been cited by other articles:

				C. A. McArdle, G. B. Willars, R. C. Fowkes, S. R. Nahorski, J. S. Davidson, and W. Forrest-Owen Desensitization of Gonadotropin-releasing Hormone Action in alpha T3-1 Cells Due to Uncoupling of Inositol 1,4,5-Trisphosphate Generation and Ca2+ Mobilization J. Biol. Chem., September 27, 1996; 271(39): 23711 - 23717. [Abstract] [Full Text] [PDF]