Vasoactive intestinal peptide causes a calcium-dependent stimulation of prolactin secretion in GH4C1 cells.
We have studied the effects of vasoactive intestinal peptide (VIP) on PRL secretion in a Bio-Gel column parafusion system containing rat pituitary tumour cells (GH4C1). A dose-dependent increase in PRL release was observed with half-maximal and maximal effect (2.1-fold) at 8 X 10(-8) and 5 X 10(-6) M, respectively. The PRL-stimulatory effect of VIP was instantaneous and maintained during the parafusion experiments (up to 60 min). On a molar basis VIP was always less effective than thyroliberin (THR), and the maximum stimulation of PRL release obtained with TRH was 1.2-3.0-fold higher (n = 12) than the maximum effect seen after VIP administration. The PRL-releasing effects of VIP, THR and high extracellular K+ were almost completely abolished in the presence of two inhibitors of voltage-sensitive Ca2+ channels, CoCl2 (10(-3) M) and verapamil (10(-4) M). In Ca2+-free buffer VIP, TRH and high extracellular K+ had only negligible effects, but the responses were fully restored in the presence of normal concentrations of extracellular Ca2+. In contrast to TRH, VIP had no demonstrable effect on the Ca2+-dependent action potentials of the GH4 cells.
D000818:Animals; D002118:Calcium / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D002460:Cell Line; D004305:Dose-Response Relationship, Drug; D004594:Electrophysiology; D010911:Pituitary Neoplasms / Q000378:metabolism*; D011188:Potassium / Q000494:pharmacology; D011388:Prolactin / Q000378:metabolism*; D051381:Rats; D013973:Thyrotropin-Releasing Hormone / Q000494:pharmacology; D014660:Vasoactive Intestinal Peptide / Q000494:pharmacology*
D014660:Vasoactive Intestinal Peptide; D013973:Thyrotropin-Releasing Hormone; D011388:Prolactin; D011188:Potassium; D002118:Calcium