Relationship between kallikrein and PRA after intravenous furosemide.

Interrelationships between plasma renin activity (PRA), urinary kallikrein and sodium excretion were studied before and after furosemide iv administration in nine normal volunteers and in one low renin non hypertensive patient. PRA, urinary kallikrein and sodium excretion increased within 15 min of furosemide injection in nine subjects; kallikrein excretion then decreased sharply, whereas plasma renin activity reached peak values within 15-120 min of stimulation. In low renin subject low basal levels of PRA paralled undetectable values of kallikrein excretion, and PRA and kallikrein excretion showed no increase after furosemide, despite the expected natriuretic response. The following conclusions appear feasible: (i) the natriuretic effect of fuorsemide is direct and independent of the effect on PRA and urinary kallikrein; (ii) in man, furosemide induces an increase in urinary kallikrein excretion which is immediate, of short duration and simultaneous in all the patient studied; (iii) no statistical correlation is demonstrated between the temporal behavior of urinary kallikrein and PRA; it is however possible that, at least for certain stimuli, renin release is in some way correlated with the activation of the renal kallikrein-bradykinin system.