Interrelation between renal kallikrein and diuresis in rats

In rats diuresis was produced by 1. furosemide (5 mg/kg/s.c.), 2. triamterene (50 mg/kg/p.o.), 3. mannitol (250 microliters, 30%) and 4. change (+ 35 mm Hg) in perfusion pressure in the isolated perfused rat kidney. In all experiments a prolonged increase in diuresis and natriuresis was effected. Urinary potassium excretion was markedly enhanced by furosemide and change in perfusion pressure, moderately increased by mannitol, and significantly depressed by triamterene. Urinary kallikrein excretion, however, showed in all of the experiments a biphasic course with an initial increase and secondary decrease. The increase of kallikrein excretion was observed only in the periods when urine flow started to increase. Thus, no correlation was found between kallikrein excretion and either urine volume or urinary sodium excretion. Kallikrein excretion correlated with potassium excretion in urine after furosemide, triamterene, and mannitol, however, it did not after increase in perfusion pressure. In renal cortical tissue kallikrein activity was reduced after all experiments, independently of the mechanisms, diuresis was induced.