Time course of the changes in active and cryoactivatable renin in response to acute stimuli before and after diuretic therapy in man

In order to elucidate whether inactive renin may represent a precursor of the active enzyme we examined the short-term effects of ambulation and of Captopril administration on active and cryoactivatable renin in patients with essential hypertension before and after 5 days of diuretic therapy. We have found that in the large majority of patients before diuretic the increments in active renin in response to these stimuli were moderate and associated with unchanged levels of cryoactivatable renin; significant decrements in cryoactivatable renin were observed only in a small group of patients in whom the increments in active renin induced by ambulation were unusually rapid and marked. Diuretic therapy caused parallel increments in baseline values of active and of cryoactivatable renin and potentiated the response of the active enzyme to ambulation and to Captopril; however, cryoactivatable renin was still unmodified during both the acute stimuli. Thus, it appears that, normally, the rise in active renin induced by ambulation and Captopril administration is associated, both before and after diuretic therapy, with unchanged levels of the inactive enzyme; however, before diuretic, abrupt increments in the demand for active renin can determine changes in opposite direction of inactive renin as if the latter were a precursor of the former.