Daily rhythmic changes in sodium-potassium activated adenosine-triphosphatase activities in rat liver and kidney.

In a systematic investigation the course of the activities of the Na-K activated ATPase and the Mg ATPase enzyme systems in rat liver and kidney were studied. In the liver the activities of both enzyme systems were on a significantly higher level (22 and 15% resp.) during the evening hours (4:00 p. m. to 2:00 a. m.). In the kidney a significantly lower level (13%) of Na-K ATPase activity was found during the night (10:00 p. m. to 8:00 a. m.), while Mg ATPase activity did not vary significantly. The periods of raised enzyme activity in liver and in kidney did not coincide. The results are discussed in relation to literature data on diurnal variations of metabolic activities in general. [ABSTRACT FROM AUTHOR]