Regulation of the (Na + + K +)-activated ATP hydrolyzing enzyme system in rat kidney. I. The effect of adrenalectomy and the supply of sodium on the enzyme system

Abstract

1. 1.Activity of the (Na + + K +)-activated ATP hydrolyzing enzyme was measured in the subcellular fractions from normal and adrenalectomized rat kidneys before and after incubation with sodium deoxycholate. 2. 2.By incubation with deoxycholate + EDTA activity of the (Na + + K +)-activated enzyme increased about 3-fold, while the activity with Mg 2+ alone remained unchanged. Using this procedure total activity of the (Na + + K +)-activated enzyme could be measured in a reproducible way. 3. 3.A 35 to 46% reduction in activity of the (Na + + K +)-activated enzyme was observed after adrenalectomy in preparations treated with deoxycholate + EDTA, while the changes in the fresh preparations were small and located in the microsomal fractions. Thus part of the decrease in activity could be ascribed to a change in response to deoxycholate of the enzyme in kidneys from adrenalectomized rats. 4. 4.The decrease in amount of the (Na + + K +)-activated enzyme during developing adrenal insufficiency corresponded to the rate of change of plasma concentrations of sodium and potassium. 5. 5.A high sodium diet could postpone and partly prevent the decrease in activity of the enzyme during developing adrenal insufficiency. This finding suggests that the enzyme is not primarily under the control of the adrenals, and might indicate an effect of sodium on activity levels of the (Na + + K +-activated enzyme in rat kidney.