[Succinate dehydrogenase and Na+-K+-ATPase activities in cells of rat kidney tubules during increased excretion of sodium, caused by furosemide].

In the cells of nephron tubules an effect of furosemide on kidney function and on succinate dehydrogenase and Na+-K+-ATPase activities was studied cytochemically. Administration of furosemide (1 mg per 100 g of body weight) increased excretion of sodium and potassium. If the rate of filtration through Malpighian tufts was constant, the increase in Na and K excretion demonstrated the tubular effect of the diuretics. Both administration of furosemide and preincubation of the drug with kidney slices in vitro caused a decrease in succinate dehydrogenase activity in the cells of all the nephron sections. These data suggest that a direct effect of the diuretics on oxidative metabolism in renal cells took place. Alteration in the activity of Na+-K+-ATPase was observed only in vivo and in those nephron sections, where sodium reabsorption was decreased under the effect of furosemide.