氯化镉对大鼠脑突触体ATP酶的影响。

Effect of cadmium chloride on rat brain synaptosomal ATPases.

作者信息

Rajanna B, Hobson M, Bansal S K, Desaiah D

出版信息

Toxicol Lett. 1983 Sep;18(3):331-6. doi: 10.1016/0378-4274(83)90114-5.

PMID:6320498

Abstract

Cadmium has been shown to alter membrane-bound ATPases both in vitro and in rats treated with the metal. However, cadmium effects on the substrate and ionic activation kinetics of Na+-K+ ATPase activity were determined by a coupled enzymatic method. A concentration-response curve was determined using 5-30 microM cadmium chloride in the reaction medium. The data showed a 50% inhibition at 15 microM cadmium chloride. Cadmium effects on ATP, Na+ and K+ activation of Na+-K+ ATPase were determined by varying the concentration of these substrates at 15 microM cadmium chloride. The double-reciprocal plots showed that cadmium inhibition of Na+-K+ was competitive with ATP and Na+ in that the Km values were increased but not the Vmax values. In contrast, cadmium inhibition was noncompetitive with K+ activation where both Km and Vmax values were decreased. The present data suggest that cadmium may be competing with ATP and Na+ sites on Na+-K+ ATPase in rat brain synaptosomes.

摘要

已表明镉在体外以及在用该金属处理的大鼠体内均会改变膜结合ATP酶。然而，通过偶联酶法测定了镉对Na⁺-K⁺ ATP酶活性的底物和离子激活动力学的影响。在反应介质中使用5 - 30微摩尔氯化镉确定浓度-反应曲线。数据显示在15微摩尔氯化镉时抑制率为50%。通过在15微摩尔氯化镉下改变这些底物的浓度，测定了镉对Na⁺-K⁺ ATP酶的ATP、Na⁺和K⁺激活的影响。双倒数图表明，镉对Na⁺-K⁺的抑制与ATP和Na⁺具有竞争性，因为Km值增加而Vmax值未增加。相反，镉抑制与K⁺激活无竞争性，此时Km和Vmax值均降低。目前的数据表明，镉可能在大鼠脑突触体中与Na⁺-K⁺ ATP酶上的ATP和Na⁺位点竞争。