The Effect of Indomethacin on Na-K-ATPase and K-pNPPase Activity of Rat Brain

ABSTRACT

The effect of indomethacin on Na-K-ATPase and K-pNPPase activity was studied with rat brain homogenate. The results were as follows : 1) Indomethacin inhibited both Na-K-ATPase and K-pNPPase in a dose-related pattern. 2) Inhibition mode of indomethacin for K+ in both Na-K-ATPase and K-pNPPase was competitive type. 3) Indomethacin showed stimulative effect at lower sodium concentration below 10mM, and showed inhibitory effect at higher sodium concentration on Na-K-ATPase and K-pNPPase activity, and the inhibitory effect was slightly increased with increasing concentration of sodium. 4) The inhibitory effect of indomethacin on Na-K-ATPase activity was increased with increasing ATP concentration, but was not affected by Mg++ concentration. These results indicate that indomethacin inhibits Na-K-ATPase activity by inhibiting K+- dependent dephosphorylation steps.