青蛙皮肤分泌氢离子的一些特征。

Some features of hydrogen (ion) secretion by the frog skin.

作者信息

Machen T, Erlij D

出版信息

Biochim Biophys Acta. 1975 Sep 16;406(1):120-30. doi: 10.1016/0005-2736(75)90047-4.

Abstract

We have studied the movements of H+ from the in vitro frog skin into the outside solution because it has been suggested that the movement of sodium from the outside solution into the skin may result from the forced exchange of Na+ by H+. Our main observations can be summarized as follows: (a) Hydrogen moves from the skin into the outside solution at a rate of 0.04 muequiv-cm-2-h-1 while Na+ influx had a value of 0.49 muequiv-cm-2-h-1. (b) The rate of H+ secretion is not significantly affected by substituting the Na+ in the outside solution by K+ nor by inhibiting Na+ influx with amiloride (5-10(-5) M). (c) Acetazolamide (5-10(-3) M) blocked H+ secretion without altering the potential difference across the skin. (d) The rate of H+ production is not underestimated because it may have been neutralized by HCO3- secreted into the outside solution in exchange for Cl-. Substituting all the Cl- by SO4(2-) in the outside solutions does not result in an increase in the rate of H+ production. (e) The steady-state rate of H+ secretion is not affected by large changes in electrochemical potential gradients for H+. Neither abolishing the potential difference across the skin nor a 10-fold change in H+ concentration in the outside solution affected significantly the steady-state rate of H+ secretion. (f) The H+ secretion was abolished by the metabolic inhibitors dinitrophenol (1-10(-4) M) and Antimycin A (1.5-10(-6) M) which also markedly reduced the potential difference across the skin. Observations (a), (b), and (c) suggest that H+ and Na+ movements across the outer border of the isolated frog skin are not coupled. The ratio of Na+ to H+ movements is very different from unity and Na+ movements can be abolished without any effects on H+ secretion and conversely H+ movements can be abolished without interruption of Na+ uptake. A second conclusion suggested by these results is that the H+ secretion does not result from movement of H+ following its electrochemical potential gradient since that rate of secretion is not affected by marked changes in either potential or [H+]. Furthermore, the effects of metabolic inhibitors suggest that H+ secretion requires the expenditure of energy by the cell.

摘要

我们研究了氢离子（H⁺）从体外青蛙皮肤进入外部溶液的运动，因为有人提出钠离子从外部溶液进入皮肤的运动可能是由H⁺对Na⁺的强制交换引起的。我们的主要观察结果可总结如下：（a）氢离子以0.04微当量·厘米⁻²·小时⁻¹的速率从皮肤进入外部溶液，而钠离子内流的值为0.49微当量·厘米⁻²·小时⁻¹。（b）用钾离子（K⁺）替代外部溶液中的钠离子，或用氨氯地平（5×10⁻⁵M）抑制钠离子内流，均不会显著影响H⁺的分泌速率。（c）乙酰唑胺（5×10⁻³M）可阻断H⁺的分泌，而不会改变皮肤两侧的电位差。（d）H⁺产生的速率不会被低估，因为它可能已被分泌到外部溶液中以交换氯离子（Cl⁻）的碳酸氢根离子（HCO₃⁻）中和。在外部溶液中用硫酸根离子（SO₄²⁻）替代所有的Cl⁻不会导致H⁺产生速率增加。（e）H⁺分泌的稳态速率不受H⁺电化学势梯度大幅变化的影响。消除皮肤两侧的电位差或使外部溶液中H⁺浓度变化10倍，均不会显著影响H⁺分泌的稳态速率。（f）代谢抑制剂二硝基苯酚（1×10⁻⁴M）和抗霉素A（1.5×10⁻⁶M）可消除H⁺的分泌，它们也显著降低了皮肤两侧的电位差。观察结果（a）、（b）和（c）表明，H⁺和Na⁺穿过离体青蛙皮肤外边界的运动没有耦合。Na⁺与H⁺运动的比率与1相差很大，消除Na⁺运动对H⁺分泌没有任何影响，反之，消除H⁺运动也不会中断Na⁺的摄取。这些结果提出的第二个结论是，H⁺的分泌不是由H⁺沿其电化学势梯度的运动引起的，因为分泌速率不受电位或[H⁺]显著变化的影响。此外，代谢抑制剂的作用表明，H⁺的分泌需要细胞消耗能量。