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The vas deferens forms part of the male reproductive tract and extends from the cauda epididymis to the prostate. Using the patch clamp technique, we have identified a Ca(2+)-activated, voltage-dependent, maxi K+ channel on the apical membrane of epithelial cells cultured from human fetal vas deferens. The channel had a conductance of approximately 250 pS in symmetrical 140 mM K+ solutions, and was highly selective for K+ over Na+. Channel activity was increased by depolarization and by an elevation of bath (cytoplasmic) Ca2+ concentration, and reduced by cytoplasmic Ba2+ (5 mM) but not by cytoplasmic TEA (10 mM). Channel activity was also dependent on the cation bathing the cytoplasmic face of the membrane, being higher in a Na(+)-rich compared to a K(+)-rich solution. We estimated that up to 600 maxi K+ channels were present on the apical membrane of a vas cell, and that their density was 1-2 per mu 2 of membrane. Activity of the channel was low on intact cells, suggesting that it does not contribute to a resting K+ conductance. However, fluid in the lumen of the human vas deferens has a high K+ concentration and we speculate that the maxi K+ channel could play a role in transepithelial K+ secretion.

Type

Journal article

Journal

J Membr Biol

Publication Date

07/1994

Volume

141

Pages

69 - 82

Keywords

Calcium, Cells, Cultured, Epithelium, Female, Fetus, Humans, Male, Patch-Clamp Techniques, Potassium, Potassium Channels, Pregnancy, Vas Deferens