Urinary excretions of kininase I and kininase II activities in essential hypertension. A sensitive and simple method for its kinin-destroying capacity.

To further clarify the role of the renal kallikrein-kinin system in essential hypertension, a sensitive and simple method for the determination of both human urinary kininase I and kininase II was established, and the system components were determined in patients. In the measurement of kininase activity, desalted urine samples were incubated with synthetic bradykinin, and the reaction was terminated with kininase inhibitors, ethylene diamine tetraacetic acid and phenanthroline. Thus, kininase activity was determined as the kinin-destroying capacity. Moreover, the specific inhibitor for kininase II, SQ14225, was applied for the separation of kininase I and kininase II activities. Daily urinary excretions of total kininase and kininase I activities were significantly higher in essential hypertensive patients than those in normotensive subjects, whereas no difference was observed in kininase II activity. As reported previously, daily excretions of urinary kallikrein and kinin simultaneously determined in these patients were significantly lower than excretions in normotensive subjects. From these results, it was suggested that not only decreased renal kallikrein, but also increased kininase activity, may play an important role in the suppression of the renal kallikrein-kinin system through the reduction of active kinin level in essential hypertension.