Role of calcium in gonadotropin releasing hormone-induced luteinizing hormone secretion from the bovine pituitary
The hypothesis was tested that GnRH acts to release LH by increasing calcium uptake by 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 (3 x 10/sup 5//well). Cells treated with GnRH Ca/sup + +/ ionophore A23187, and ouabain all produced significant releases of LH release in a pronounced all or none fashion, while thorough washing of the cells with 0.5 mM EGTA in Ca/sup + +/-free media prevented the action of GnRH. GnRH caused a rapid efflux of /sup 45/Ca/sup + +/. Both GnRH-stimulated /sup 45/Ca efflux and LH release could be partially blocked by verapamil GnRH-induced LH release could also be blocked by nifedipine and tetrodotoxin, although these agents did not affect /sup 45/Ca efflux. The calmodulin antagonists calmidazolium and W7 were found to block GnRH induced LH release, as well as LH release induced by theophylline, KC PGE/sub 2/ and estradiol. These data indicated that: (1) calcium is required for GnRH action, but extracellular Ca/sup + +/ does not regulate LH release; (2) GnRH elevates intracellular Ca/sup + +/ by opening both voltage sensitive and receptor mediated Ca/sup + +/ channels; (3) activation of calmodulin is one mechanism involved in GnRH-induced LH release.
- Research Organization:
- Texas A and M Univ., College Station (USA)
- OSTI ID:
- 7063506
- Resource Relation:
- Other Information: Thesis (Ph. D.)
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
CALCIUM 45
UPTAKE
CALCIUM COMPOUNDS
LH
CHEMICAL ACTIVATION
SECRETION
CALVES
CATTLE
GONADOTROPINS
LIBERINS
PITUITARY GLAND
ALKALINE EARTH ISOTOPES
ALKALINE EARTH METAL COMPOUNDS
ANIMALS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BODY
CALCIUM ISOTOPES
DAYS LIVING RADIOISOTOPES
DOMESTIC ANIMALS
ENDOCRINE GLANDS
EVEN-ODD NUCLEI
GLANDS
HORMONES
INTERMEDIATE MASS NUCLEI
ISOTOPES
MAMMALS
NUCLEI
ORGANS
PEPTIDE HORMONES
PITUITARY HORMONES
RADIOISOTOPES
RUMINANTS
VERTEBRATES
551001* - Physiological Systems- Tracer Techniques