Molecular Pharmacology, Vol 15, 525-530, Copyright © 1979 by the American Society for Pharmacology and Experimental Therapeutics

Effect of Angiotensinase Inhibitors on Angiotensin Receptors in Rabbit Aorta

¹ Department of Pharmacology, University of Montreal P. O. B. 6128, Montreal, Quebec, Canada H3C 3J7

Caproic acid (1 cM) and EDTA (10 mM) blocked the cell membrane angiotensinase of rabbit aorta. Caproic acid significantly increased the maximal response to angiotensin and delayed the relaxation time of contracted aortic strips. EDTA decreased the maximal response and had no effect on relaxation. This was attributed to EDTA chelating capacity for Ca ions. The binding studies revealed an increased angiotensin receptor binding in the presence of antiotensinase inhibitors. The increased maximal response and delayed relaxation time observed with caproic acid might be due to uncovering of additional angiotensin receptors and increased agonist availability at the receptor site after angiotensinase blockade. This in turn stimulates some post-receptor mechanism leading to increased intracellular Ca²⁺.