Biology of Reproduction, Vol 50, 49-54, Copyright © 1994 by Society for the Study of Reproduction

ARTICLES

Differential secretion of follicle-stimulating hormone and luteinizing hormone from ovine pituitary cells following activation of protein kinase A, protein kinase C, or increased intracellular calcium

JP Kile and TM Nett
Animal Reproduction and Biotechnology Laboratory, Colorado State University, Fort Collins 80523.

A higher dose of GnRH is required to stimulate release of FSH than of LH, both in vivo and in vitro. Therefore, we tested the hypothesis that secretion of FSH may be mediated via a second messenger pathway different from the one that modulates secretion of LH. Pituitary cells from intact ewes were cultured in suspension in DMEM plus 10% wether serum. After 18 h, cell were washed and challenged for 2 h with agents capable of activating protein kinase A (dibutyryl cAMP), protein kinase C (phorbol 12-myristate 13-acetate; PMA), or increasing intracellular calcium (the calcium ionophore A23187). GnRH (0.01-10 nM) and PMA (0.2- 20 nM) stimulated dose-dependent increases in secretion of LH. FSH secretion also was stimulated by GnRH and PMA; however, the percentage of total cellular FSH released was lower (p < 0.05) than the percentage of total cellular LH released. Dibutyryl cAMP (10 mM) induced a modest release (p < 0.05) of both LH and FSH. A23187 (1-10 microM) stimulated secretion of LH in a dose-dependent manner but did not influence secretion of FSH; however, GnRH- and PMA-induced secretion of FSH required the presence of intracellular calcium. On the basis of the results of this study, we suggest that secretion of FSH is less than secretion of LH following direct activation of these second messenger systems. Furthermore, we suggest that in contrast to the situation for LH, increased intracellular calcium is not the primary stimulus for inducing secretion of FSH.

This article has been cited by other articles:

				C. A Lents, N. L Heidorn, C R. Barb, and J J. Ford Central and peripheral administration of kisspeptin activates gonadotropin but not somatotropin secretion in prepubertal gilts Reproduction, June 1, 2008; 135(6): 879 - 887. [Abstract] [Full Text] [PDF]

				I. J. Clarke, V. A. Tobin, S. Pompolo, and A. Pereira Effects of Changing Gonadotropin-Releasing Hormone Pulse Frequency and Estrogen Treatment on Levels of Estradiol Receptor-{alpha} and Induction of Fos and Phosphorylated Cyclic Adenosine Monophosphate Response Element Binding Protein in Pituitary Gonadotropes: Studies in Hypothalamo-Pituitary Disconnected Ewes Endocrinology, March 1, 2005; 146(3): 1128 - 1137. [Abstract] [Full Text] [PDF]

				C. Molter-Gérard, J. Fontaine, S. Guérin, and C. Taragnat Differential Regulation of the Gonadotropin Storage Pattern by Gonadotropin-Releasing Hormone Pulse Frequency in the Ewe Biol Reprod, May 1, 1999; 60(5): 1224 - 1230. [Abstract] [Full Text]