INHIBITION OF RENAL ADENOSINE-TRIPHOSPHATASE BY CADMIUM

Abstract

The effects of CdCl2 on ATPase were studied in microsomal fractions or tissue homogenates of outer cortex, inner cortex and outer medulla of dog kidney. Cd was found to be an inhibitor of Na+ + K+ ATPase with 150 [50% maximum inhibition] value of 2.1-3.2 .times. 10-4 M regardless of type or source of the enzyme preparation tested. Mg++ ATPase was about 10-fold less sensitive to inhibition by Cd than Na+ + K+ ATPase. The inhibition of microsomal NA+ + K+ ATPase from outer medulla was characterized by irreversible kinetics. The inhibitory effect was not altered by varying Na+ or K+ concentrations, but was decreased by EDTA. EDTA was more effective in preventing than in reversing the inhibition. Na+ + K+ ATPase from kidneys of several other mammalian spp. [rat, rabbit, cat, guinea pig, sheep, mouse] showed a similar sensitivity to Cd.