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

J. V. Milligan and Jacob Kraicer
Science
New Series, Vol. 167, No. 3915 (Jan. 9, 1970), pp. 182-184
Stable URL: http://www.jstor.org/stable/1728936
Page Count: 3
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Adenohypophysial Transmembrane Potentials: Polarity Reversal by Elevated External Potassium Ion Concentration
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Abstract

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.

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