Role of ATPase activated by Mg ++ in the Na + and K + dependent ATPase enzyme system of the rat small intestine

Abstract

Role of the Mg-activated ATPase in the Enzymatic ATPase System Depending on Na+ and K+ from the Small Intestine of Rat

The Na-K ATPase activity of a Miller and Crane type fraction from mucosa of rat small intestine has been studied. It has been followed under several ionic conditions the course of reaction in the time. The action of Ca++, the influence of ATP concentration and the effects of ouabaine and other inhibitory agents have been also tested.

The relation of the ATPase activity in the presence of Mg++, Na+, K+ to that a with only Mg++, changes with the reac­ tion time, showing a máximum between 10 and 25 minutes and decreasing after wards for a longer time. Ca44" inhibits the depending on Na and K activity.

Ouabaine inhibits the preparation from intestinal mucosa though less than those from other sources. A similar inhibition has been however observed when the pre­paration is previously incubated with the glucoside. Other cardiotonic drugs (PBGH and PLBGH) proved to have a higher inhibitory power than ouabaine. The Sys­tem is also inhibited by sodium azide.

Several results suggest that the ATPase residual activity in the presence of Mg4-4' could be merely due to a functional deficiency of the same system operating with also Na+ and K+ in the médium.