Increased urine angiotensin I converting enzyme activity in patients with upper urinary tract infection.

Angiotensin converting enzyme (ACE) is present within the brush border of the tubular cell of the kidney. Since it has a high molecular mass, ACE activity of urine most probably derives only from tubular cells, thus suggesting the potential usefulness of ACE determination as an index of tubular damage. When assayed with the method described, ACE is optimally active at pH 8 with a calcium concentration exceeding 0.