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Subcellular localization in rat brain of angiotensin-related carboxypeptidase activity distinct from converting
D G Changaris1, N W Lesousky, J J Miller
1Department of Surgery (Division of Neurological Surgery), University of Louisville School of Medicine, Ky.
Abstract:
Whole brain synaptosomes contain both an isorenin activity and angiotensin-related carboxypeptidase activity. Further hydrolysis of des-Leu angiotensin I (AI-dL) occurs more slowly; hydrolysis of angiotensin II (AII) is negligible. Vasopressin and oxytocin but not vasotocin can inhibit angiotensin-related carboxypeptidase activity. Since AII has been shown to induce vasopressin secretion, this correlation suggests a feedback inhibition by vasopressin of this enzymatic cascade. Commercially available radioimmunoassays for AI and AII show a 3.4 and 6.0% crossreactivity, respectively. When the absolute concentration of AI-dL exceeded 500 ng/ml, both antibodies to AI and AII showed maximal displacement of radiolabel. This suggests that these antibodies may not distinguish between AI-dL from other peptides during immunocytochemistry.