Effect of metabolic inhibitors on urine osmolality and electrolyte excretion

The in vivo effects of aerobic and anaerobic metabolic inhibitors on renal Na and K transport and concentrating ability were studied in dogs. Two aerobic inhibitors (sodium cyanide and hydroxylamine) and two anaerobic inhibitors (iodoacetate and triethyleneiminotriazine) were infused into one renal artery. Urine was collected separately from both kidneys and urine osmolality, Na, and K concentrations were measured. In addition, stop-flow experiments were done before and after infusion of NaCN and iodoacetate into one renal artery. Aerobic inhibitors resulted in a decrease in urine osmolality associated with a large increase in Na excretion. Anaerobic inhibitors resulted in a similar decrease in urine osmolality with only a minimal increase in Na excretion. In stop-flow experiments cyanide blocked Na and K transport in the distal tubule. Iodoacetate had no demonstrable effect on distal Na or K transport, but did abolish K secretion which was presumed to take place in the collecting ducts. These results suggest that Na and K transport in medullary regions is largely dependent on energy derived from anaerobic glycolysis.