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

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dc.contributor.advisorAmoss, Max S.
dc.contributor.committeeMemberJenkins, William L.
dc.contributor.committeeMemberMacKenzie, Duncan S.
dc.contributor.committeeMemberMcConnell, Stewart
dc.creatorKile, Jay Perry
dc.date.accessioned2020-09-02T21:04:24Z
dc.date.available2020-09-02T21:04:24Z
dc.date.issued1986
dc.descriptionTypescript (photocopy).en
dc.description.abstractThe 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.en
dc.format.digitalOriginreformatted digitalen
dc.format.extentx, 175 leavesen
dc.format.mediumelectronicen
dc.format.mimetypeapplication/pdf
dc.identifier.oclc17967716
dc.identifier.urihttps://hdl.handle.net/1969.1/DISSERTATIONS-22005
dc.language.isoeng
dc.publisher.digitalTexas A&M University. Libraries
dc.rightsThis thesis was part of a retrospective digitization project authorized by the Texas A&M University Libraries. Copyright remains vested with the author(s). It is the user's responsibility to secure permission from the copyright holder(s) for re-use of the work beyond the provision of Fair Use.en
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/
dc.subjectMajor veterinary physiologyen
dc.subject.classification1986 Dissertation K48
dc.subject.lcshLuteinizing hormone releasing hormoneen
dc.subject.lcshGonadotropinen
dc.subject.lcshCalciumen
dc.subject.lcshCattleen
dc.subject.lcshPhysiologyen
dc.titleThe role of calcium in gonadotropin releasing hormone-induced luteinizing hormone secretion from the bovine pituitaryen
dc.typeThesisen
dc.type.genredissertationsen
dc.type.materialtexten
thesis.degree.grantorTexas A&M Universityen
thesis.degree.nameDoctor of Philosophyen
thesis.degree.namePh. Den

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