[Beta-adrenergic receptivity and left ventricular hypertrophy caused by pressure overload in man]

The effect of left ventricular chronic pressure overload on right atrial (RA) and left ventricular (LV) myocardial beta-adrenoceptor (beta-AR) density and subtypes ([I125] cyanopindolol binding), adenylate cyclase activity (AC) and ADP-pertussis toxin ribosylated proteins was investigated in 13 patients with aortic stenosis (AO) and compared with the results obtained in 10 patients with mitral stenosis (MI) taken as controls. None of the patients included had any impairement of systolic function or increased plasma catecholamine levels. The total number of beta-AR in RA (62 +/- 6 vs 77 +/- 12 fmoles/mg prot) and LV (39 +/- 7 vs 32 +/- 2 fmoles/mg prot) was similar in AO and in MI. The percentage of beta 1-AR was significantly lower in LV from AO (35 +/- 11 vs 73 +/- 5% in MI) but identical in RA (79 +/- 5 vs 73 +/- 8%). The basal activity of AC was similar in membranes from patients with AO (19 +/- 4 and 22 +/- 5 pmol.mg-1 prot in RA and LV) and in controls (21 +/- 6 and 27 +/- 3 pmol.mg-1 prot in RA and LV). Isoprenaline-induced stimulation of AC was significantly lower in LV membranes from patients with AO (7 +/- 6 vs 45 +/- 6% in MI) but remained identical in RA membranes (51 +/- 18 vs 36 +/- 18% in MI). The quantification of ADP-pertussis toxin ribosylated proteins indicated a lower substrate concentration in myocardial membranes from patients with AO when compared with controls.(ABSTRACT TRUNCATED AT 250 WORDS)