Prevention of angiotensin II induced myocyte necrosis and coronary vascular damage by lisinopril and losartan in the rat.

OBJECTIVE

The aims were to determine: (1) if angiotensin converting enzyme (ACE) inhibition and angiotensin II receptor blockade can prevent angiotensin II induced coronary vascular damage; (2) if the cardioprotective properties of ACE inhibition are dose dependent; and (3) if the cardioprotective properties of ACE inhibition are independent of its ability to prevent the conversion of angiotensin I to angiotensin II.

METHODS

Control rats and rats with either renovascular hypertension or continuous angiotensin II infusion (150 ng.min-1) for 14 d were subdivided into nine groups as follows: unoperated and untreated controls (n = 5); untreated renovascular hypertension (n = 8); untreated angiotensin II (n = 9); a renovascular hypertension group receiving one of the following doses of lisinopril 20 (n = 8), 2.5 (n = 4), and 0.6 (n = 6) mg.kg-1.d-1; a renovascular hypertension group receiving losartan (7.5 mg.d-1, n = 4); and an angiotensin II group receiving either the high dose of lisinopril (n = 6) or losartan (n = 4). Treatment was started one day before initiation of renovascular hypertension and angiotensin II infusion and continued throughout the study period. The number and size of necrotic areas and numbers of damaged coronary vessels were determined in sections of right and left ventricular tissue.

RESULTS

Both coronary vascular injury and myocyte injury induced by angiotensin II were prevented by losartan. In renovascular hypertension, the lowest dose of lisinopril prevented vascular and attenuated myocyte damage but to a lesser degree than the higher doses. The cardioprotective ability of ACE inhibition is primarily the result of its ability to prevent the conversion of angiotensin I to angiotensin II.

CONCLUSIONS

Angiotensin II related cardiomyocyte necrosis and coronary vascular damage are angiotensin type 1 receptor mediated and completely preventable with the receptor antagonist losartan. The ability of ACE inhibition to prevent this damage is dose dependent and primarily related to the degree to which the inhibitor can prevent the conversion of angiotensin I to angiotensin II.