help button home button Endocrine Society Endocrinology
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
This Article
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow Request Copyright Permission
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Hunzicker-Dunn, M.
Right arrow Articles by LaBarbera, A. R.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Hunzicker-Dunn, M.
Right arrow Articles by LaBarbera, A. R.

Endocrinology, Vol 118, 302-311, Copyright © 1986 by Endocrine Society

ARTICLES

Unique properties of the follicle-stimulating hormone- and cholera toxin-sensitive adenylyl cyclase of immature granulosa cells

M Hunzicker-Dunn and AR LaBarbera

Previous studies have shown that the adenylyl cyclase of intact granulosa cells from immature porcine follicles has a uniquely prolonged responsiveness to FSH and an atypically poor responsiveness to cholera toxin relative to other cells. The present studies were designed to determine if these characteristics were due to unique regulation of the adenylyl cyclase activation process by Mg2+ and guanine nucleotides. GTP and Mg2+ enhanced adenylyl cyclase activity in the absence and presence of FSH in a manner similar to that in other systems. For example, GTP and Mg2+ increased the maximal velocity rather than the sensitivity of the cyclase to GTP and Mg2+. However, several unique properties distinguish the FSH-sensitive adenylyl cyclase from other hormonally activated adenylyl cyclases. First, FSH did not increase the sensitivity of the enzyme to Mg2+; thus the apparent Km for Mg2+ remained nonphysiologically high in the presence of FSH. Second, FSH was only one fourth as effective as NaF in activating the enzyme. Third, maximal activity attained in the presence of NaF was very low relative to that in other cells. Fourth, even in the presence of exogenous NAD+, cholera toxin activated adenylyl cyclase only as well as FSH rather than as well as NaF. Fifth, instead of causing maximal activation in the absence of stimulator, guanyl-5'- ylimidodiphosphate enhanced by almost 2-fold basal, FSH-activated, and cholera toxin-activated adenylyl cyclase. The inability of either guanyl-5'-ylimidodiphosphate or cholera toxin alone to cause maximal activation of the guanine nucleotide-binding protein, as reflected by cyclase activity, indicates that guanine nucleotide binding in the absence of hormone or cholera toxin is limiting.


This article has been cited by other articles:


Home page
 EndocrinologyHome page
F. Harandian and R. Farookhi
Contact-Dependent Cell Interactions Determine Hormone Responsiveness and Desensitization in Rat Granulosa Cells
Endocrinology, April 1, 1998; 139(4): 1700 - 1707.
[Abstract] [Full Text] [PDF]


HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
Endocrinology Endocrine Reviews J. Clin. End. & Metab.
Molecular Endocrinology Recent Prog. Horm. Res. All Endocrine Journals
Copyright © 1986 by The Endocrine Society