The effect of local converting enzyme inhibition on the dilator response to substance P in the human forearm.

It has been proposed that angiotensin converting enzyme (ACE) may play a part in the metabolism of substance P. Reduced metabolism following treatment with ACE inhibitors may cause accumulation of substance P to produce the adverse effect of cough. It has been shown in this study that, in contrast to angiotensin I and bradykinin, inhibition of local vascular ACE does not interfere with the vascular effects of substance P on forearm resistance vessels when this peptide is infused into the brachial artery of normal volunteers. These results suggest that endothelial ACE plays little part in the metabolism of intravascular substance P.