Urinary kallikrein in postobstructive diuresis

We studied urinary kallikrein excretion in the rat during unilateral release of 24-hr bilateral ureteral ligation (BUL). In six rats studied after 24 hr of BUL, the glomerular filtration rate was 20 per cent of that in the five sham-operated controls. In the BUL group, the urine flow rate was 5 fold greater, fractional sodium excretion 100 times greater, and fractional potassium excretion 5 times greater than in controls. Urinary kallikrein excretion in the BUL group was one-half that of the controls. However, urinary kallikrein excretion per functioning nephron was increased 3 fold in the BUL group. Five of six BUL rats with increased fractional sodium and water excretion also showed increased urinary kallikrein excretion/GFR when compared to controls. Our study suggests that after 24 hr of BUL in the rat, urinary kallikrein excretion is increased in relation to the remaining, functioning nephrons and suggests a role for the kallikrein-kinin system in the postobstructive salt and water losses.