Blood kinin system in renal hypertensive patients administered with SQ 20881

The i.v. administration of 0.25 mg/kg SQ 20881 to eight renal hypertensive patients caused blood pressure fall and in five of them also reduced heart rate. The latter was attributed to increase in vagal tone. Peripheral and renal blood samples taken at the nadir of the hypotensive response showed considerable inhibition of plasma kininase activity, rise in free kinin level and reduced kininogen content. This reduction was not due to increased consumption as shown by in vitro experiments. PGE2 and PGF2 alpha levels in kidney blood of three patients remained practically unchanged. Plasma renin activity was augmented to a larger extent in blood of kidney with stenotic artery than in the one with patent vessel. It is concluded that the action of SQ 20881 on human blood kinin system, besides inhibition of kininase, involves also reduction of kininogen, the mechanism of which remains to be clarified.