The role of calcium in gonadotropin releasing hormone-induced luteinizing hormone secretion from the bovine pituitary /

Bibliographic Details
Main Author: Kile, Jay Perry, 1956-
Other Authors: Jenkins, William L. (degree committee member.), MacKenzie, Duncan S. (degree committee member.), McConnell, Stewart (degree committee member.)
Format: Thesis Book
Language:English
Published: 1986.
Subjects:
Online Access:Link to ProQuest copy
Link to OAKTrust copy
ProQuest, Abstract

MARC

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099 |a 1986  |a Disser-  |a tation  |a K48 
100 1 |a Kile, Jay Perry,  |d 1956- 
245 1 4 |a The role of calcium in gonadotropin releasing hormone-induced luteinizing hormone secretion from the bovine pituitary / 
264 1 |c 1986. 
300 |a x, 175 leaves :  |b illustrations ;  |c 29 cm 
336 |a text  |b txt  |2 rdacontent 
337 |a unmediated  |b n  |2 rdamedia 
338 |a volume  |b nc  |2 rdacarrier 
500 |a "Major subject: Veterinary Physiology." 
500 |a Typescript (photocopy). 
500 |a Vita. 
502 |b Ph. D.  |c Texas A & M University  |d 1986 
504 |a Includes bibliographical references (leaves 117-158). 
520 3 |6 520-00  |a The hypothesis was tested that GnRH acts to release LH by increasing calcium uptake by the gonadotroph which in turn stimulates calcium-calmodulin activity and results in LH release from bovine pituitary cells as it does in the rat. Pituitary glands of calves (4-10 months of age) were enzymatically dispersed (0.2% collagenase) and grown for 5 days to confluency in multiwell plates (3x10^5/well). Cells treated with GnRH (10-1000 ng/ml in Hank's Balanced Salt Solution), Ca++ ionophore A23187 (2.5-10 μM), and ouabain (0.1-1 μM) all produced significant releases of LH. Extracellular Ca++ as low as 46 μM permitted GnRH-induced LH release in a pronounced "all or none" fashion, while thorough washing of the cells with 0.5 mM EGTA in Ca++-free media prevented the action of GnRH. GnRH (100 ng/ml) caused a rapid efflux (15 seconds) of ^45Ca++. Both GnRH-stimulated 45Ca efflux and LH release could be partially blocked by verapamil (10^-5 M). GnRH-induced LH release could also be blocked by nifedipine (10^-7-10^-5 M) and tetrodotoxin (10^-9 10^-7 M), although these agents did not affect 45Ca efflux. The calmodulin antagonists calmidazolium (10^-9-10^-8M) and W7 (10^-6-10^-5 M) were found to block GnRH induced LH release, as well as LH release induced by theophylline (1 mM), KC1 (25 mM), PGE2 (1 μM) and estradiol (25 ng/ml). These data indicated that: (1) calcium is required for GnRH action, but extracellular Ca++ does not regulate LH release; (2) GnRH elevates intracellular Ca++ by opening both voltage sensitive and receptor mediated Ca++ channels; (3) activation of calmodulin is one mechanism involved in GnRH-induced LH release. 
650 0 |a Calcium. 
650 0 |a Cattle  |x Physiology. 
650 0 |a Gonadotropin. 
650 0 |a Luteinizing hormone releasing hormone. 
650 4 |a Major veterinary physiology. 
655 7 |a Academic theses  |2 lcgft 
700 1 |a Amoss, Max S.,  |e degree supervisor. 
700 1 |a Jenkins, William L.,  |e degree committee member. 
700 1 |a MacKenzie, Duncan S.,  |e degree committee member. 
700 1 |a McConnell, Stewart,  |e degree committee member. 
710 2 |a Texas A & M University,  |e degree granting institution. 
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