In Vivo Measurements of Local Metabolic Rate in the Dog Kidney. Effect of Mersalyl, Chlorothiazide, Ethacrynic Acid and Furosemide

Abstract

The initial rate of temperature rise during arterial occlusion was measured with fine thermocouples placed in the kidney of anesthetized dogs for estimation of local metabolic rate. Experimental evaluation of the necessary assumptions indicated the method to be applicable in the cortex and outer medulla. Since renal metabolism seems mainly determined by tubular reabsorption of sodium, the method can be used to localize the natriuretic action of diuretics. Mersalyl reduced metabolic rate per unit tissue volume of the outer medulla to 65% of control without significant reduction in the cortex, indicating inhibition of sodium transport in the loops of Henle. Chlorothiazide lowered cortical metabolic rate to 76% of control, with no change in outer medulla, indicating an action in the convoluted tubules. Ethacrynic acid and furosemide acted mainly in the loops of Henle, as indicated by reduction of outer medullary metabolic rate to 21 and 32% of control values respectively. Cortical metabolic rate fell to 78 and 85% of control, suggesting additional effect in cortical nephron segments. Swelling of the kidney during diuresis may account for a reduction in metabolic rate per unit tissue volume of about 10% of control.