乙醇与（钠钾）-ATP 酶：钠钾选择性的改变

Ethanol and (Na+,K+)-ATPase: alteration of Na(+)-K+ selectivity.

作者信息

Swann A C

机构信息

Department of Psychiatry, University of Texas Medical School, Houston 77225.

出版信息

Alcohol Clin Exp Res. 1990 Dec;14(6):922-7. doi: 10.1111/j.1530-0277.1990.tb01839.x.

DOI:10.1111/j.1530-0277.1990.tb01839.x

PMID:1965100

Abstract

Relative internal concentrations of Na+ and K+ are important in regulating (Na+,K+)-ATPase in situ. Ethanol is known to inhibit (Na+,K+)-ATPase and to reduce K+ affinity, but the concentrations required for these effects in vitro are large compared with those probably attainable in vivo. Yet, there is evidence suggesting that ethanol has physiologically relevant effects on (Na+,K+)-ATPase. We have investigated the effects of ethanol on selectivity for Na+ versus K+. At 150 mM, ethanol had little effect on (Na+,K+)-ATPase activity under the usual assay conditions, slightly (but nonsignificantly) reduced K+ affinity, and had no effect on extrapolated Na+ affinity in the absence of K+. However, ethanol had marked effects on cation selectivity, doubling the Ki for K+ on Na+ affinity and halving the Ki for Na+ on K+ affinity. These data show that ethanol, at concentrations too small for effects on (Na+,K+)-ATPase activity under optimal assay conditions, can alter its responses to changes in Na+ or K+.

摘要

Na⁺和K⁺的相对胞内浓度对于原位调节（Na⁺，K⁺）-ATP酶很重要。已知乙醇会抑制（Na⁺，K⁺）-ATP酶并降低K⁺亲和力，但与体内可能达到的浓度相比，体外产生这些效应所需的浓度很高。然而，有证据表明乙醇对（Na⁺，K⁺）-ATP酶具有生理相关效应。我们研究了乙醇对Na⁺与K⁺选择性的影响。在150 mM时，在通常的测定条件下乙醇对（Na⁺，K⁺）-ATP酶活性几乎没有影响，略微（但不显著）降低了K⁺亲和力，并且在不存在K⁺的情况下对外推的Na⁺亲和力没有影响。然而，乙醇对阳离子选择性有显著影响，使K⁺对Na⁺亲和力的抑制常数（Ki）加倍，而使Na⁺对K⁺亲和力的Ki减半。这些数据表明，在最佳测定条件下，乙醇浓度低至对（Na⁺，K⁺）-ATP酶活性无影响时，仍可改变其对Na⁺或K⁺变化的反应。