Sohma Y, Harris A, Wardle C J, Gray M A, Argent B E
Department of Physiological Sciences, University Medical School, Newcastle upon Tyne, United Kingdom.
J Membr Biol. 1994 Jul;141(1):69-82. doi: 10.1007/BF00232875.
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.
输精管是男性生殖道的一部分，从附睾尾部延伸至前列腺。运用膜片钳技术，我们在人胎儿输精管培养的上皮细胞顶膜上鉴定出一种钙激活、电压依赖性的大电导钾通道。在对称的140 mM钾溶液中，该通道的电导约为250 pS，对钾的选择性远高于钠。通道活性因去极化和胞外（胞质）钙浓度升高而增强，因胞质钡（5 mM）而降低，但不受胞质四乙铵（10 mM）影响。通道活性还取决于膜胞质面所接触的阳离子，与富含钾的溶液相比，在富含钠的溶液中活性更高。我们估计，每个输精管细胞的顶膜上存在多达600个大电导钾通道，其密度为每平方微米膜1 - 2个。在完整细胞上，该通道的活性较低，这表明它对静息钾电导没有贡献。然而，人类输精管管腔内的液体具有高钾浓度，我们推测大电导钾通道可能在跨上皮钾分泌中发挥作用。
