A rapid, Ca2+-independent, onset of prostaglandin E2 stimulation of the release of luteinizing hormone releasing hormone from copper-treated median eminence explants.
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)
Barnea
A
A
Department of Obstetrics, University of Texas Southwestern Medical Center, Dallas 75235.
Bhasker
K R
KR
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
D007987:Gonadotropin-Releasing Hormone; D004533:Egtazic Acid; D003300:Copper; D015232:Dinoprostone; D002118:Calcium