Selective ETA receptor blockade prevents left ventricular remodeling and deterioration of cardiac function in experimental heart failure.

BACKGROUND: Left ventricular (LV) dilation, which is a predictor of survival in humans with chronic heart failure (CHF), is limited by a mixed endothelin ETA-ETB antagonist. Whether selective ETA receptor blockade influences LV dilation is unknown. We determined, in a rat model of CHF, the effects of the ETA receptor blocker LU 135,252 on LV remodeling. METHODS AND
RESULTS: Rats were subjected to coronary artery ligation and treated for ten weeks with placebo or LU 135,252 (LU), at a dose of 10 or 30 mg kg-1 day-1. Systolic blood pressure and heart rate (plethysmography) were determined in conscious animals before and after four and ten weeks of treatment. At these time points, cardiac output and LV dimensions were measured in anesthetized rats by transthoracic echocardiography. LV hemodynamics were determined in anesthetized rats after ten weeks. Pressor responses to ET-1 (1 nmol/kg, i.v.) and sarafotoxin S6c (0.3 ng/kg, i.v.) were measured, to assess the efficacy of ET receptor antagonism and the lack of blockade of ETB receptor blockade, respectively. The pressor response to ET-1 was significantly reduced by LU (% change in systolic blood pressure: sham: 9 +/- 1; CHF: 5 +/- 1; CHF LU: 0 +/- 3 and -4 +/- 2% for the low and high dose, respectively). LU did not affect the response to sarafotoxin (CHF: -37 +/- 3; CHF LU: -29 +/- 3 and -28 +/- 2% for the low and high dose, respectively). Both doses of LU decreased systolic blood pressure, but only the high dose of LU reduced heart rate. Furthermore, LU restored cardiac output dose-dependently throughout the study. Both doses of LU limited LV dilatation and deterioration of LV fractional shortening to the same extent. After ten weeks, LU normalized LV end-diastolic- and central venous pressures, but did not affect LV dP/dtmax or dP/dtmin. LU did not prevent the development of cardiac hypertrophy, but reduced LV collagen density.
CONCLUSIONS: In this rat model, the selective ETA receptor blocker LU, at the dose of 30 mg kg-1 day-1, reduced blood pressure and heart rate, limited progressive left ventricular remodeling and improved cardiac hemodynamics and function. These effects of LU might have important clinical relevance in the treatment of heart failure.