Urinary kallikrein: assay validation and physiological variability.

Decreased urinary kallikrein (UK) output has been suggested as a preclinical indicator of essential hypertension. In preparation for UK studies in hypertension prone Utah kindreds, we assessed selected UK assay parameters and physiological variability. Precision for the colorimetric kallikrein assay was quite acceptable, coefficient of variation (CV) less than 5% within run and 14% day-to-day at a concentration of 9.5 TU/l. The mean recovery was 105% and assay results were correlated with results from the 3H-TAME esterase method, r = 0.990. Urine specimens were stable at room temperature for up to 4 days, frozen at -20 degrees C for 6 weeks, or frozen at -80 degrees C after Sephadex treatment for a year. UK output varied significantly throughout the day with excretion highest in the morning. Urine collections at 10.00, 12.00 and 14.00 had significantly (p less than 0.05) more UK than the overnight collection. Intra- and inter-individual variations were of the same magnitude, mean 20%. In children UK output increased with age until the adult levels were reached at age 15. Male and female values were similar. Smoking; consumption of alcohol, coffee, tea, cola of chocolate; and female hormone medications did not significantly influence the 12-hour UK output in the 1110 caucasian subjects.