Interrelationship between urinary kallikrein and arginine-vasopressin in man

Physiological saline solution was infused in 9 normal subjects and 6 patients with central diabetes insipidus (DI). At 120 min after the start of infusion, arginine vasopressin (AVP) was injected (i.m.). Urine was collected every 30 min fraction. The urinary excretion of kallikrein-like activity (KAL-A) (S-2266 hydrolysis activity) was significantly lower in patients with DI than in normal subjects, without showing the differences of plasma renin activity (PRA), plasma aldosterone concentration (PAC), creatinine clearance (Ccr) and blood pressure between the two groups, except a marked water-diuresis in DI. The urinary excretion of KAL-A correlated positively with the urinary excretion of AVP. AVP administration significantly increased the urinary excretion of KAL-A. After overnight fasting, an acute oral water-loading was carried out for 15 min in 6 normal subjects. Concomitant with a significant suppression of the level of plasma AVP from the first 30 min, a slight, but significant, decrease in urinary excretion of KAL-A was observed in the first 30 min fraction after loading, compared with the control period. Afterwards, the urinary excretion of KAL-A increased prominently with an increase in urine flow. KAL-A in the urine decreased promptly from the first 30 min fraction and then gradually until 120 min after loading. Urine volume and free-water markedly increased except the first 30 min fraction, compared with the control period. Thus it is suggested that AVP is one of factors which actually regulate the secretion of renal kallikrein in man.