Des-Asp1-angiotensin I: a metabolite of angiotensin I in the perfused feline adrenal.

The administration of radioactive angiotensin I to the retrogradely perfused feline adrenal gland caused a brisk discharge of catecholamines. Recovery of the labelled decapeptide and metabolites in the adrenal effluent fluid was complete in 5 min. Radioimmunoassay of this perfusate revealed that most of the peptide remained as angiotensin I, but chromatographic and electrophoretic evaluation indicated that greater than 68% of the peptide had been metabolized to des-asp1 -angiotensin I. The absence of des-asp1 -angiotensin II, angiotensin II or his-3H-leu in adrenal effluent fluid suggested minimal dipeptidyl carboxypeptidase activity in this preparation. In addition, the profile of angiotensin I metabolites from the perfused adrenal was not altered by treatment with a converting enzyme inhibitor B. jararaca nonapeptide. The des-asp1-angiotensin I peptide was a very weak secretagogue in the adrenal medulla. If metabolism of the decapeptide to the nonapeptide occurs in the medulla, this may represent a pathway to limit the secretory action of angiotensin I. These results suggest a high degree of adrenal aminopeptidase activity which may be primarily localized in the adrenal cortex.