Pulmonary angiotensin-converting enzyme. Interspecies homology and inhibition by heterologous antibody in vivo

Abstract

Goat antibody against pure rabbit pulmonary angiotensin-converting enzyme was used to probe homology of converting enzymes from other species. Immunologically cross-reactive material was found in detergent-solubilized extracts of lung particles from rat, guinea pig, and dog by double immunodiffusion, radioimmunoassay, and inhibition of enzyme activity. No homology was demonstrable with bovine, frog, or chicken lung extracts. Antibodies from different individual goats yielded comparable estimates of homology by immunodiffusion and radioimmunoassay. In contrast, they varied greatly in extent and specificity of their inhibitory action on heterologous enzyme activity. The vasopressor effect of angiotensin I and the vasodepressor effect of bradykinin were diminished and potentiated, respectively, in rats treated with anti-rabbit enzyme antibody. A smaller but significant immune-dependent inhibition of the vasopressor response to angiotensin II was also observed.