Adrenoceptor recovery after heart failure in the dog

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Abstract
Objective: The role of myocardial β receptors in pacing induced congestive heart failure is uncertain. The aims of the study were therefore (1) to examine total β adrenoceptor density in canine left ventricle during pacing induced heart failure; and (2) to evaluate whether there is a relationship between β adrenoceptor numbers and circulating noradrenaline during progression of heart failure. Methods: Heart failure was examined at different stages: early (after 1 week of pacing at 250 beats·min−1); peak (after 4 weeks of pacing); and after recovery (4 weeks after pacing was discontinued). Myocardial β adrenoceptor density was assessed by radioligand binding with iodocyanopindolol. Plasma noradrenaline was determined by high performance liquid chromatography with electrochemical detection. Results: Compared to control, left ventricular β adrenoceptor density was: (1) not significantly different in early heart failure, at 2540(SEM 460) v 3160(260) fmol·g−1 wet weight in control; (2) decreased 63% at peak heart failure [1180(100) fmol·g−1, prestored to control density after recovery from heart failure [3430(540) fmol·g−1]. The β adrenoceptor dissociation constant was unaltered throughout. There was an inverse correlation between myocardial β adrenoceptor density and plasma noradrenaline (r = −0.785, pConclusions: The progressive decline in β adrenoceptor density as heart failure develops and the capacity of β adrenoceptors to return to control levels after recovery from the experimental heart failure state suggests that there is a reversible abnormality in β adrenoceptors during heart failure. Cardiovascular Research 1993;27:489-493

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