Calcium influx is not required for thyrotropin-releasing hormone stimulation of prolactin release from GH3 cells.
TRH stimulation of prolactin release from GH3 cells is dependent on Ca2+; however, whether TRH-induced influx of extracellular Ca2+ is required for stimulated secretion remains controversial. We studied prolactin release from cells incubated in medium containing 110 mM K+ and 2 mM EGTA which abolished the electrical and Ca2+ concentration gradients that usually promote Ca2+ influx. TRH caused prolactin release and 45Ca2+ efflux from cells incubated under these conditions. In static incubations, TRH stimulated prolactin secretion from 11.4 +/- 1.2 to 19 +/- 1.8 ng/ml in control incubations and from 3.2 +/- 0.6 to 6.2 +/- 0.8 ng/ml from cells incubated in medium with 120 mM K+ and 2 mM EGTA. We conclude that Ca2+ influx is not required for TRH stimulation of prolactin release from GH3 cells.
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002460:Cell Line; D002462:Cell Membrane / Q000502:physiology; D007700:Kinetics; D008564:Membrane Potentials / Q000187:drug effects; D009374:Neoplasms, Experimental / Q000378:metabolism / Q000503:physiopathology; D010911:Pituitary Neoplasms / Q000378:metabolism* / Q000503:physiopathology; D011188:Potassium / Q000494:pharmacology; D011388:Prolactin / Q000378:metabolism*; D051381:Rats; D013973:Thyrotropin-Releasing Hormone / Q000494:pharmacology*
D013973:Thyrotropin-Releasing Hormone; D011388:Prolactin; D011188:Potassium; D002118:Calcium