Evidence that Ca(2+)-activated K+ channels participate in the regulation of pituitary prolactin secretion.
We evaluated the role of Ca(2+)-activated K+ channels in the regulation of prolactin (PRL) secretion with a perifusion system using acutely dispersed rat anterior pituitary cells. Apamin, which blocks Ca(2+)-activated K+ channels, induced PRL secretion in a dose-dependent fashion between 1 and 300 nM (r = 0.99, P < 0.01). Charybdotoxin, another Ca(2+)-activated K+ channel-blocker, also induced PRL secretion at 20 nM concentration. These were not non-specific toxic effects, since stimulation of PRL secretion by 10 nM thyrotropin-releasing hormone (TRH) was not different before and after applying the channel-blockers. Both 10 microM dopamine and 2 microM nifedipine significantly, but incompletely, depressed PRL secretion induced by 100 nM apamin; 10 microM dopamine completely blocked PRL secretion induced by 20 nM charybdotoxin. Our data indicate that Ca(2+)-activated K+ channels may play an important role in the regulation of PRL secretion.
Wang
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Department of Physiology, Oregon Health Sciences University, Portland 97201.
Inukai
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Greer
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Greer
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D000818:Animals; D001030:Apamin / Q000037:antagonists & inhibitors / Q000494:pharmacology; D002118:Calcium / Q000502:physiology*; D018999:Charybdotoxin; D004298:Dopamine / Q000494:pharmacology; D066298:In Vitro Techniques; D008297:Male; D009543:Nifedipine / Q000494:pharmacology; D010903:Pituitary Gland, Anterior / Q000166:cytology / Q000378:metabolism / Q000502:physiology*; D015221:Potassium Channels / Q000502:physiology*; D011388:Prolactin / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012604:Scorpion Venoms / Q000037:antagonists & inhibitors / Q000494:pharmacology; D013973:Thyrotropin-Releasing Hormone / Q000378:metabolism
D015221:Potassium Channels; D012604:Scorpion Venoms; D018999:Charybdotoxin; D001030:Apamin; D013973:Thyrotropin-Releasing Hormone; D011388:Prolactin; D009543:Nifedipine; D002118:Calcium; D004298:Dopamine