Adenohypophysial Transmembrane Potentials: Polarity Reversal by Elevated External Potassium Ion Concentration

Science  09 Jan 1970:
Vol. 167, Issue 3915, pp. 182-184
DOI: 10.1126/science.167.3915.182


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.