Effect of cyanide on renal metabolic rate and glomerulotubular balance

Measurements of anesthetized dogs by the heat-accumulation technique showed that cyanide reduced equally the metabolic rates of outer medulla and cortex, whereas combined infusion of ethacrynic acid and chlorothiazide reduced mainly the metabolic rate of the outer medulla. During ethacrynic acid and chlorothiazide infusion, cyanide reduced the remaining sodium reabsorption by an average of 19% and the remaining cortical metabolic rate by 43%, but had no additional effect on the outer medullary metabolism. Metabolic rates remained essentially constant when glomerular filtration rate (GFR) was raised during cyanide infusion from 63 plus or minus 3 to 135 plus or minus 7% of control by carotid constriction or intravenous infusion of angiotensin. Glomerulotubular balance, defined as proportional relationship between sodium reabsorption and GFR during infusion of ethacrynic acid and chlorothiazide, was present only at GFR less than 80% of control in experiments with and without cyanide infusion. We conclude that cyanide inhibits proximal energy-requiring sodium transport which cannot be inhibited by ethacrynic acid and chlorothiazide, but does not alter the range of GFR over which glomerulotubular balance applies.