title: A rapid, Ca2+-independent, onset of prostaglandin E2 stimulation of the release of luteinizing hormone releasing hormone from copper-treated median eminence explants.
abstract: Prostaglandin E2 (PGE2) is known to stimulate the release of luteinizing hormone releasing hormone (LHRH) from explants of the median eminence area (MEA). We have previously shown that a short preincubation of the MEA with copper markedly amplifies PGE2 stimulation of LHRH release and that the Ca2+-cAMP pathway is involved in this release process. In this study, we defined the kinetics of the onset of PGE2 action and examined the Ca2+ requirement for the onset and manifestation of PGE2 action. MEA explants from immature female rats were incubated with copper (150 microM copper-histidine complex); thereafter, explants were exposed to 10 microM PGE2 for periods of 2-7 min with or without Ca2+ (Ca2+-free buffer containing 1 mM EGTA). A 2 min PGE2 exposure was as effective as a 7 min PGE2 exposure in stimulating LHRH release; the latter was manifested during the period between 2-7 min. When MEA were exposed to PGE2 for 5 min, maximal rate of release was attained within this 5 min period. When MEA were exposed to PGE2 for 2 min and then to forskolin (100 microM) for 5 min, there was no further increase in the rate of LHRH release (although exposure to forskolin alone maximally stimulated LHRH release). In the presence of EGTA (no Ca2+), PGE2 stimulation of LHRH release was abolished and this effect of EGTA was totally reversed by the addition of Ca2+ 2 min after PGE2 exposure and partially reversed (40%) by the addition of Ca2+ 5 min after PGE2 exposure in the presence of EGTA.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Obstetrics, University of Texas Southwestern Medical Center, Dallas 75235.
authors.forename: A
authors.initials: A
authors.lastname: Barnea
authors.forename: K R
authors.initials: KR
authors.lastname: Bhasker
mesh_terms: D000818:Animals; D002118:Calcium / Q000502:physiology*; D003300:Copper / Q000494:pharmacology; D015232:Dinoprostone / Q000494:pharmacology*; D004533:Egtazic Acid / Q000494:pharmacology; D005260:Female; D007987:Gonadotropin-Releasing Hormone / Q000378:metabolism*; D066298:In Vitro Techniques; D008473:Median Eminence / Q000378:metabolism*; D011863:Radioimmunoassay; D051381:Rats; D011919:Rats, Inbred Strains; D013997:Time Factors
chemical_list: D007987:Gonadotropin-Releasing Hormone; D004533:Egtazic Acid; D003300:Copper; D015232:Dinoprostone; D002118:Calcium