Perindopril Effects on Angiotensin I Elimination in Lung After Experimental Myocardial Injury Induced by Intracoronary Microembolization in Rats

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The objective of the study was to determine whether angiotensin (Ang) I elimination in lung circulation depends on the degree of myocardial damage with and without early long-term perindopril treatment in a rat model of myocardial injury induced by intracoronary microembolization. Twenty-one days after surgery, steady-state arterial [125I]-Ang I and [125I]-Ang II blood concentrations were measured after high-performance liquid chromatography separation during i.v. infusion of [125I]-Ang I in three groups of male Wistar conscious rats: (a) sham-operated rats receiving saline (sham group, n = 6); (b) rats after coronary microembolization receiving saline (saline group, n = 7); and (c) rats after coronary microembolization receiving perindopril (2 mg/kg/day; from days 2-20 after embolization; perindopril group, n = 6). Ang I clearance and the Ang I-to-Ang II concentration ratio (R) were estimated. The embolization per se resulted in focal fibrosis, appearance of hypertrophic and dystrophic cardiac myocytes, and was accompanied by increased Ang I clearance (1,479 vs. 314 ml/min in sham group), 1.8-fold decreased [125I]-Ang II arterial level, and decreased R (0.5 vs. 1.2 in sham group; p < 0.05). Only Ang I concentrations and R were correlated with number of scars (r = −0.77; p < 0.05; and r = −0.82; p < 0.01, respectively). Captopril bolus (1 mg/kg, i.v.) caused similar reduction in [125I]-Ang II blood concentration in both sham and saline groups, but a significant increase of [125I]-Ang I blood concentration was detected in the sham group only. Thus in rats with coronary microembolization, a higher proportion of Ang I in lung circulation is eliminated by pathways independent of angiotensin-converting enzyme. In the perindopril group, a reduced number of scars (seven vs. 17 per slice in the saline group; p < 0.05), density of dystrophic and hypertrophic cardiac myocytes, and increased content of cell glycogen were observed. It was accompanied by normalized arterial [125I]-Ang I concentration, Ang I clearance, and R; [125I]-Ang II concentration tended to that in sham group. Only in the sham and perindopril groups was there significant correlation between Ang I and Ang II concentrations. The clear relation between number of scars per slice and R (r = −0.83; p < 0.01) was observed in all rats with embolized coronary vessels (saline and perindopril groups together). In conclusion, in this experimental, model Ang I elimination in the lung circulation was directly related to the degree of myocardial damage. Early perindopril treatment prevented maladaptive changes in Ang I processing and led to significant reduction of the undesirable aftereffects of myocardial tissue damage. Our data demonstrate the cardioprotective action of perindopril based on its beneficial influence on the renin-angiotensin system disturbances.

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