Quantitative and qualitative estimation of urinary kallikrein in a patient with Bartter's syndrome

Urinary kallikrein in a patient with Bartter's syndrome was remarkably higher than normal. Indomethacin treatments increased serum potassium concentration and urinary Na/K ratio, and improved the response of blood pressure to angiotensin II infusion, while it decreased plasma renin activity, plasma aldosterone and urinary kallikrein. The purified urinary kallikrein had one component of the iso-electric point 4.3 by isoelectric focusing using Ampholine system, and its molecular weight was 4.2 x 10(4), which was greater than those of three components of normal human urinary kallikreins (normal HUK). Also Km values with TAME and BAME of urinary kallikrein in our patient with Bartter's syndrome did not correspond to those of normal HUK. Thus it can be said that urinary kallikrein in our patient with Bartter's syndrome was qualitatively different from normal HUK. The present observation might be a reflection of renal tubular dysfunction in this patient with Bartter's syndrome.