Modulation of presynaptic sympathetic activity by kinins and related compounds: influence of converting enzyme inhibition.

Since converting enzyme and kininase II are identical enzymes and probably influences both, the biosynthesis of Ang II and the metabolism of bradykinin we investigated the effects of bradykinin, desArg-bradykinin and some bradykinin antagonists (desArg[9]-Leu[8]-bradykinin, HOE S 890307) on the sympathetic outflow of pithed SHR or Brown-Norway-Rats before and after acute or chronic inhibition of the converting enzyme by ramipril. bradykinin increased dose dependently the noradrenaline and adrenaline release in particular when the converting enzyme was inhibited. DesArg-bradykinin caused a dose-dependent increase in adrenaline release only after converting enzyme inhibition. The bradykinin-antagonists led to an increase in adrenaline release during ramipril administration. The weak but significant stimulation of adrenaline release by the bradykinin antagonists after converting enzyme inhibition might be due to unspecific actions on the adrenal medulla possibly induced by histamine release from mast cells.