Evidence that potassium channels regulate prolactin secretion in GH4C1 cells by causing extracellular calcium influx.
Tetraethylammonium (TEA), a K+ channel blocker, induced prolactin (PRL) secretion in GH4C1 cells in a dose-dependent manner when applied at a concentration from 1-20 mM. During continuous exposure to TEA, a significant increase in PRL secretion occurred by 20 min and the response was sustained until the end of a 60-min exposure. Blocking Ca2+ influx by employing a Ca(2+)-depleted medium or the Ca2+ channel blocker, nifedipine, prevented induction of PRL secretion by 20 mM TEA. Preincubation of the cells for 10 min with 20 mM TEA did not inhibit PRL secretion induced by thyrotropin-releasing hormone (TRH), phorbol 12-myristate 13-acetate (TPA) or by cell swelling produced by 30% medium hyposmolarity, but significantly depressed that induced by depolarizing 30 mM K+. BaCl2, another K+ channel blocker, had the same effect on PRL secretion as TEA. The data suggest that blocking K+ channels may cause membrane depolarization, thereby inducing Ca2+ influx which is a potent stimulus for PRL secretion in GH4C1 cells.
Department of Medicine, Oregon Health Sciences University, Portland 97201.
X B
XB
Wang
N
N
Sato
M A
MA
Greer
S E
SE
Greer
S
S
McAdams
D002118:Calcium / Q000378:metabolism*; D002463:Cell Membrane Permeability / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D006801:Humans; D009543:Nifedipine / Q000494:pharmacology; D015221:Potassium Channels / Q000187:drug effects / Q000502:physiology*; D011388:Prolactin / Q000037:antagonists & inhibitors / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D019789:Tetraethylammonium; D013757:Tetraethylammonium Compounds / Q000494:pharmacology; D013973:Thyrotropin-Releasing Hormone / Q000494:pharmacology; D014407:Tumor Cells, Cultured
D015221:Potassium Channels; D013757:Tetraethylammonium Compounds; D013973:Thyrotropin-Releasing Hormone; D019789:Tetraethylammonium; D011388:Prolactin; D009543:Nifedipine; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium