LACK OF EFFECT OF CHRONIC CALCIUM-ANTAGONIST TREATMENT ON BETA-1-ADRENOCEPTORS AND BETA-2-ADRENOCEPTORS IN RIGHT ATRIA FROM PATIENTS WITH OR WITHOUT HEART-FAILURE

1 We studied the effects of chronic calcium antagonist (calcium entry blocker, CEB; nifedipine, verapamil, diltiazem) treatment on beta-adrenoceptor density (assessed by (-)-[I-125]-iodocyanopindolol [ICYP] binding) and subtype distribution in right atria from 65 patients without apparent heart failure undergoing elective coronary artery bypass grafting (CAD-patients) and from 13 patients with moderate heart failure (NYHA class III to class III-IV) undergoing mitral valve replacement (MVD-patients). 2 In CAD-patients atrial beta-adrenoceptor density was 79.3 +/- 7.9 fmol ICYP bound mg-1 protein (n = 18), the beta(1):beta(2)-adrenoceptor ratio 69:31%. Chronic CEB-treatment did not affect either atrial beta-adrenoceptor density or beta(1):beta(2)-adrenoceptor ratio. 3 In contrast, in CAD-patients chronically treated with beta(1)-adrenoceptor antagonists (atenolol, bisoprolol, metoprolol) and CEB, atrial beta-adrenoceptor density was significantly increased (108.6 +/- 10.5 fmol ICYP bound mg-1 protein, n = 21); this increase was due to a selective increase in beta(1)-adrenoceptors. 4 In MVD-patients atrial beta-adrenoceptor density (55.5 +/- 8.7 fmol ICYP bound mg-1 protein, n = 7) was significantly lower (P < 0.05) than in CAD-patients; beta(1):beta(2)-adrenoceptor ratio, however, was not changed (67:33%). Chronic CEB-treatment of MVD-patients did not prevent the decrease in atrial beta-adrenoceptors. 5 We conclude that chronic CEB-treatment does not affect human right atrial beta-adrenoceptor density, either in patients without apparent heart failure or in patients with moderate heart failure. In addition, the increase in atrial beta(1)-adrenoceptors caused by chronic beta(1)-adrenoceptor antagonist treatment seems not to be affected by simultaneous CEB-treatment.