Immunotitration of alkaline phosphatase isozymes in normal and pathological urine.

Isoenzyme patterns of alkaline phosphatase are determined quantitatively in extracts of human kidney as well as in human urine by means of immunotitration technique. Both media contain two types of AP isoenzymes: liver and intestinal like AP. Intestinal AP is located as a minor component of total AP activity (1-4%) in particle-free fraction of the kidney. Urinary AP activity is found after high speed centrifugation in supernatant (100,000 Xg) as well as in the 100,000 Xg sediment and can only be made soluble from the latter by n-butanol treatment. Intestinal AP in urine is concentrated in the supernatant while in sediment the isoenzyme pattern resembles to that of kidney. Urine of normal persons contains most of AP activity in the sediment and consists mainly of liver type AP. Urinary AP of patients with renal diseases or after application of cytotoxins contains little sedimentable activity, mainly intestinal AP.