Comparative effects of a novel angiotensin-converting enzyme inhibitor versus captopril on plasma angiotensins after myocardial infarction

The compound 4-tert-butyl-2,6-bis(thiomorpholin-4-ylmethyl)phenol (TBTIF) has molecular characteristics similar to angiotensin-converting enzyme (ACE) inhibitors of the sulfhydryl subclass. To assess its value as a new therapeutic agent, we performed a comparative analysis of the effect of TBTIF versus captopril on the circulating levels of angiotensin (Ang) peptides and bradykinin as well as ACE and ACE2 expression after myocardial infarction. Male Wistar rats were divided into four groups: (1) sham-operated rats; (2) rats subjected to 48 h of coronary artery ligation; (3) rats administered captopril (1 mg/kg, i.m.), and (4) a similar group of rats given TBTIF (1 mg/kg, i.m.). Both drugs were administered 30 min before coronary artery ligation and again 24 h later. Acute myocardial infarction lowered both systolic and left ventricular systolic blood pressures compared to the sham group and increased plasma levels of Ang I, Ang II, Ang(1-7) and Ang(1-12). Administration of either captopril or TBTIF reversed the increases in plasma angiotensins. Interestingly, the levels of plasma Ang(1-7) achieved by administration of TBTIF reached values higher than those recorded with captopril. Both agents reversed the decreases in plasma concentrations of bradykinin; in addition, TBTIF upregulated ACE expression, while both agents suppressed the ACE2 upregulation induced by myocardial infarction. These results demonstrate a beneficial effect of the novel compound TBTIF in suppressing the acute surge in the circulating renin-angiotensin system activity induced by myocardial infarction. The greater effects of this compound in augmenting plasma Ang(1-7) concentrations may be highly significant as drugs which augment the concentration of this heptapeptide will exert cardioprotective actions in part by suppressing the hypertrophic and profibrotic actions of Ang II.