Expression and significance of β adrenergic receptors in a model of left ventricular mechanical unloading

Abstract

To study the expression and significance of β adrenergic receptors mRNA in a model of left ventricular mechanical unloading, and explore the change in cardiomyocyte in molecular level after left ventricular unloading. Heart failure was reproduced in Lewis rats by ligating left anterior descending (LAD) artery. After 4 weeks, the failing hearts and right lungs were heterotopically transplanted into the abdomen of the recipients by anastomosing their ascending aorta to the recipients' descending aorta in the heart transplantation group. Two weeks after transplantation, heart weight, left ventricular weight, myocyte diameter and myocardial fibrosis were determined , and β adrenergics receptors mRNA expression was essayed by real-time polymerase chain reaction (PCR). Seven normal Lewis rats served as control. The weight of the enlarged heart, left ventricular weight and myocyte diameter of the failing hearts were decreased to normal after transplantation. The levels of β1- and β2- adrenergic receptors mRNA expression were significantly lowered in heart failure group compared with that of normal group(0.09 ± 0.03 vs. 0.18 ± 0.04, 0.07 ± 0.06 vs. 0.12 ± 0.02, both P <0.05). The level of β2- adrenergic receptor mRNA expression in heart transplantation group (0.11 ± 0.05) rose to normal (P>0.05), but β1- adrenergic receptor mRNA expression (0.08 ± 0.06) was lower in heart transplantation group than that in normal group (P<0.05). Myocardium reverse remodeling after left ventricular unloading is accompanied by the change in cardiomyocyte in molecular level , such as the change in β adrenergic receptors , which may involve in the improvement of heart function after being supported by left ventricular assist device.