text: Role of extracellular calcium and calmodulin in prolactin secretion induced by hyposmolarity, thyrotropin-releasing hormone, and high K+ in GH4C1 cells.
  The mechanism by which 30% medium hyposmolarity induces PRL secretion by GH4C1 cells was compared with that induced by 100 nmol/l TRH or 30 mmol/l K+. Removing medium Ca2+, blocking Ca2+ channels with 50 mumol/l verapamil, or inhibiting calmodulin activation with 20 mumol/l trifluoperazine, 10 mumol/l chlorpromazine or 10 mumol/l pimozide almost completely blocked hyposmolarity-induced secretion. The smooth muscle relaxant, W-7, which is believed relatively specific in inhibiting the Ca2(+)-calmodulin interaction, depressed hyposmolarity-induced PRL secretion in a dose-dependent manner (r = -0.991, p less than 0.01). The above drugs also blocked or decreased high K(+)-induced secretion, but had much less effect on TRH-induced secretion. Secretion induced by TRH, hyposmolarity, or high K+ was optimal at pH 7.3-7.65 and was significantly depressed at pH 6.0 or 8.0, indicating that release of hormone induced by all 3 stimuli is due to an active cell process requiring a physiologic extracellular pH and is not produced by nonspecific cell toxicity. The data suggest hyposmolarity and high K+ may share some similarities in their mechanism of stimulating secretion, which is different from that of TRH.
entities.id: T10 T11 T12 T13 T14 T15 T16 T17 T18 T19 T1 T20 T21 T22 T23 T24 T25 T26 T2 T3 T4 T5 T6 T7 T8 T9
entities.type: CHEMICAL CHEMICAL CHEMICAL CHEMICAL CHEMICAL GENE-Y GENE-Y GENE-N GENE-Y GENE-Y CHEMICAL GENE-Y GENE-Y GENE-Y GENE-Y GENE-Y GENE-Y GENE-Y CHEMICAL CHEMICAL CHEMICAL CHEMICAL CHEMICAL CHEMICAL CHEMICAL CHEMICAL
entities.text: Ca2(+) K(+) K+ K+ calcium TRH TRH Ca2+ channels calmodulin calmodulin K+ PRL PRL TRH TRH calmodulin prolactin thyrotropin-releasing hormone K+ Ca2+ Ca2+ verapamil trifluoperazine chlorpromazine pimozide W-7