Different angiotensin II-forming pathways in human and fat vascular tissues

We studied the angiotensin II-forming pathways in extracts from human and r at vascular tissues. In the extract from human artery, angiotensin I mainly converted to two products, angiotensin-(l-9) and angiotensin II, while in the extract from rat artery, the major angiotensin I products were angioten sin II and angiotensin-(5-10), The concentrations of angiotensin II and ang iotensin-(l-9) generated in the human extract (1 mg protein/ml) after incub ation for 30 min were 3.2 and 2.5 nmol, respectively, and that of angiotens in II and angiotensin-(5-10) generated in the rat extract (1 mg protein/ml) were 0.28 and 2.3 nmoI, respectively. In the extract from human vascular t issues, the angiotensin II formation was inhibited by 8% with lisinopril an d by 95% with chymostatin. The other product, angiotensin-(l-9) was inhibit ed completely by carboxypeptidase inhibitor. In the extract from rat vascul ar tissues, the angiotensin II formation was suppressed to 4% by lisinopril , but not by chymostatin. The angiotensin-(5-10) formation was completely i nhibited by chymostatin. These findings suggest clearly that human vascular tissues contain two angiotensin II-forming enzymes, angiotensin-converting enzyme and chymase, but rat vascular tissues have no chymase-dependent ang iotensin II-forming pathway. (C) 2001 Elsevier Science B.V. All rights rese rved.