Reversal of angiotensin-(1–12)-caused positive modulation on left ventricular contractile performance in heart failure: Assessment by pressure-volume analysis

Abstract

BackgroundAngiotensin-(1–12) [Ang-(1–12)] is a renin-independent precursor for direct angiotensin-II production by chymase. Substantial evidence suggests that heart failure (HF) may alter cardiac Ang-(1–12) expression and activity; this novel Ang-(1–12)/chymase axis may be the main source for angiotensin-II deleterious actions in HF. We hypothesized that HF alters cardiac response to Ang-(1–12). Its stimulation may produce cardiac negative modulation and exacerbate left ventricle (LV) systolic and diastolic dysfunction. Methods and resultsWe assessed the effects of Ang-(1–12) (2 nmol/kg/min, iv, 10 min) on LV contractility, LV diastolic filling, and LV-arterial coupling (AVC) in 16 SD male rats with HF-induced by isoproterenol (3 mo after 170 mg/kg sq. for 2 consecutive days) and 10 age-matched male controls. In normal controls, versus baseline, Ang-(1–12) increased LV end-systolic pressure, without altering heart rate, arterial elastance (EA), LV end-diastolic pressure (PED), the time constant of LV relaxation (τ) and ejection fraction (EF). Ang-(1–12) significantly increased the slopes (EES) of LV end-systolic pressure (P)-volume (V) relations and the slopes (MSW) of LV stroke wok-end-diastolic V relations, indicating increased LV contractility. AVC (quantified as EES/EA) improved. In contrast, in HF, versus HF baseline, Ang-(1–12) produced a similar increase in PES, but significantly increased τ, EA, and PED. The early diastolic portion of LV PV loop was shifted upward with reduced in EF. Moreover, Ang-(1–12) significantly decreased EES and MSW, demonstrating decreased LV contractility. AVC was decreased by 43%. ConclusionsIn both normal and HF rats, Ang-(1–12) causes similar vasoconstriction. In normal, Ang-(1–12) increases LV contractile function. In HF, Ang-(1–12) has adverse effects and depresses LV systolic and diastolic functional performance.