Endogenous inhibitor of angiotensin converting enzyme in the rat heart

Abstract We have identified a substance in the rat heart which inhibits ACE. This substance was characterized to be a sulfhydryl(SH) protein, the SH moiety being essential for the inhibitory activity. The inhibitory activity disappeared when the extract was boiled, or the ultrafiltrate(mol.wt. −8 M ANG I was inhibited by 60%. This endogenous inhibitor of ACE may modulate the activity of ACE in the heart, in response to alterations in the oxidation-reduction balance in the tissue.