Effect of ACE inhibitor on DOCA-salt- and aortic coarctation-induced hypertension in mice: do kinin B2 receptors play a role?

Kinins have been shown to play an important role in the cardioprotective effect of ACE inhibitors (ACEi) during heart failure and ischemia-reperfusion. However, it is controversial as to whether kinins oppose the hypertensinogenic effect of deoxycorticosterone acetate plus salt (DOCA-salt) or aortic coarctation and whether they mediate both chronic antihypertensive and cardiac antihypertrophic effects of ACEi in hypertension. Using normal 129/SvEvTac mice and mice lacking the bradykinin B2 receptor gene (B2-KO), we investigated whether (1) the hypertensinogenic effect of DOCA-salt or aortic coarctation is enhanced in B2-KO mice and (2) the chronic antihypertensive and antihypertrophic effects of an ACEi (ramipril, 4 mg. kg-1. d-1) are mediated by B2 receptors in aortic coarctation (6 weeks)- and DOCA-salt (4 weeks)-induced hypertension. Before surgery, there was no difference between 129/SvEvTac and B2-KO mice in terms of blood pressure and heart weight, suggesting that kinins are not essential to maintaining normal blood pressure. DOCA-salt (volume expansion) or aortic coarctation (renin-dependent) induced similar hypertension and left ventricular hypertrophy (LVH) in 129/SvEvTac and B2-KO mice, suggesting that kinins do not play an essential role in the development of DOCA-salt- or aortic coarctation-induced hypertension. We found that B2 receptors mediate only the early (1 week) but not the late phase (4 weeks) of the chronic hypotensive effect of ACEi in DOCA-salt hypertension. On the other hand, chronic ACE inhibition prevented the development of hypertension and LVH in both 129/SvEvTac and B2-KO mice given DOCA-salt or subjected to aortic coarctation, suggesting that kinins do not participate in the chronic antihypertensive and antihypertrophic effects of ACEi in these 2 models of hypertension. Thus, in mice, kinins acting via B2 receptors do not participate in (1) maintenance of normal basal blood pressure, (2) establishment and maintenance of hypertension induced by DOCA-salt or aortic coarctation, and (3) chronic antihypertensive and cardiac antihypertrophic effects of ACEi in DOCA-salt and aortic coarctation hypertension.