RÉSUMÉ
<p><b>OBJECTIVE</b>To observe the effect of beta(3)-adrenoceptor (AR) in regulating resting intracellular Ca(2+) concentration of the ventricular myocytes and investigate the signaling pathway in rats with experimental heart failure.</p><p><b>METHODS</b>Rat models of experimental heart failure were established by ligation of the anterior descending artery, and the myocytes were isolated by enzymatic digestion. The resting intracellular Ca(2+) concentration was determined using laser scanning confocal microscopy (LSCM) in the cells stimulated with 1 micromol/L BRL37344 (a selective beta(3)-AR agonist) alone or in combination with PTX, L-NAME, or methylene blue.</p><p><b>RESULTS</b>In the ventricular myocytes from normal control rats, BRL373444 reduced the resting intracellular Ca(2+) concentration of by 45.5%, while the reduction increased to 59.4% in the cells from rats with heart failure. In combination with L-NAME (10 micromol/L), methylene blue (10 micromol/L), and PTX (2 microg/ml), BRL373444 caused a reduction in resting intracellular Ca(2+) concentration of the ventricle myocytes from normal control rats by 10.1%, 16.9%, and 15.4%, respectively in control group, while the rate was 16.9%, 19.3%, and 11.7% in the heart failure group.</p><p><b>CONCLUSIONS</b>Beta(3)-AR agonist can decrease the resting intracellular Ca(2+) concentration of the ventricular myocytes, but the reduction is smaller in cells from rats with heart failure than in cells of normal rats. This effect is mediated through the PTX-NOS-NO pathway.</p>