Prolactin secretion in permeable GH3 pituitary cells is stimulated by Ca2+ and protein kinase C activators.
We have used GH3 cells permeabilized by electric field discharge to examine the effects of Ca2+ and protein kinase C activators (phorbol ester and diacylglycerol) on prolactin (PRL) release. Ca2+ was found to stimulate PRL release approximately 4 fold at 3 microM Ca2+ with a half-maximal response at approximately .5 microM estimated free Ca2+. 12-O-tetradecanoyl phorbol-13-acetate and 1-oleoyl-2-acetyl-sn-glycerol stimulated PRL release throughout a range of Ca2+ concentrations (1 nM -3 microM), but stimulation was greater at higher Ca2+ concentrations (.1 microM to 1 microM). Both agents decreased by 1.8 fold the apparent [Ca2+] at which half-maximal stimulation of secretion occurred. Quin 2 was used to measure the free [Ca2+] of intact and permeable cells; PRL secretion at a free [Ca2+] corresponding to resting cytoplasmic [Ca2+] was 10% of maximal, while secretion at the [Ca2+] corresponding to the Ca2+ spike induced by thyrotropin-releasing hormone was approximately 25% of maximal.
Ronning
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SA
Martin
T F
TF
D000634:Aminoquinolines; D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D002460:Cell Line; D002463:Cell Membrane Permeability; D003593:Cytoplasm / Q000201:enzymology; D004075:Diglycerides / Q000494:pharmacology; D004789:Enzyme Activation; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D010902:Pituitary Gland / Q000187:drug effects / Q000378:metabolism*; D010911:Pituitary Neoplasms / Q000378:metabolism; D011388:Prolactin / Q000378:metabolism*; D011493:Protein Kinase C; D011494:Protein Kinases / Q000378:metabolism*; D051381:Rats; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013973:Thyrotropin-Releasing Hormone / Q000494:pharmacology
D000634:Aminoquinolines; D004075:Diglycerides; D013973:Thyrotropin-Releasing Hormone; C038237:1-oleoyl-2-acetylglycerol; D011388:Prolactin; D007770:L-Lactate Dehydrogenase; D011494:Protein Kinases; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate; C035739:Quin2; D002118:Calcium