A SUSTAINED INCREASE IN BETA-ADRENOCEPTORS DURING LONG-TERM THERAPY WITH METOPROLOL AND BISOPROLOL IN PATIENTS WITH HEART-FAILURE FROM IDIOPATHIC DILATED CARDIOMYOPATHY

Effects of long-term therapy with beta(1)-selective antagonists (metop rolol, bisoprolol) on beta-adrenoceptors in lymphocytes of patients wi th idiopathic dilated cardiomyopathy (DCM) were examined. There was a significant reduction in the number of lymphocyte beta-adrenoceptors i n patients with DCM compared to that in healthy volunteers, as demonst rated by a selective decrease in maximum number of binding sites (Bmax ) for (-)-[I-125]iodocyanopindolol (CYP). A therapy with metoprolol an d bisoprolol in these patients caused a marked increase in lymphocyte beta-adrenoceptor density. The significant increase was observed from 2 or 3 months after the start of therapy with these drugs, and it was maintained during the therapy for 24 months. The left ventricular ejec tion fraction in patients with DCM was improved by the long-term thera py with metoprolol and bisoprolol, and this effect seems to be correla ted with an observed enhancement of lymphocyte beta-adrenoceptors in t he time course. Also, the increase in lymphocyte beta-adrenoceptors ap pears to be correlated with a gradual amelioration in circulating cate cholamine levels by the long-term therapy with beta-adrenoceptor antag onists in patients with DCM. Thus, the present study suggests that bet a-adrenoceptors in lymphocytes of patients with DCM are up-regulated b y a long-term therapy with metoprolol and bisoprolol.