Adenohypophysial transmembrane potentials: polarity reversal by elevated external potassium ion concentration.
Incubation of rat adenohypophyses in potassium ion of sufficient concentration to provoke the release of several of the adenohypophysial trophic hormones produces a reversed, positive transmembrane potential in more than half the cells. This finding is consistent with a process of "stimulus-secretion coupling" in which hypothalamic releasing factors act by selective depolarization of their "target" cells. The positive potentials may be due to a prolonged preferential permeability to calcium ions triggered by an initial depolarization of the cell membrane to a threshold value by increased external potassium ion.
D000818:Animals; D002463:Cell Membrane Permeability; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects*; D010902:Pituitary Gland; D010906:Pituitary Hormone-Releasing Hormones; D011188:Potassium / Q000494:pharmacology*; D051381:Rats
D010906:Pituitary Hormone-Releasing Hormones; D011188:Potassium