Effect of β3-Adrenergic Receptor on Atrial L-type Ca2+ Current in Rats with Chronic Heart Failure

Objectives To investigate the effect of selective beta(3)-adrenoreceptor agonist BRL-37344 on L-type Ca2+ current (I-ca,L) and mRNA expression of L-type Ca2+ channel alpha(2)delta-2 (Cacna2d2) in rats with chronic heart failure (CHF). Methods Twenty-four male Wistar rats were divided into normal control (n =6) and CHF group (n = 18), which were further divided into CHF control and BRL group (0.4 nmol/kg, IV, twice weekly for four weeks). Echocardiography was performed to assess the structure and function of the left atrium (LA). Results The LA in the BRL group (4.4 +/- 0.2 mm) was larger than in the normal control (3.5 +/- 0.3 mm, P < 0.01) or CHF control (4.0 +/- 0.2 mm, P < 0.05) group. The LA ejection fraction in the BRL group (36.2 +/- 4.2%) was lower than in the normal control (58.0 +/- 3.1%, P <0.01) or CHF control group (42.3 +/- 4.8%, P < 0.05). There was no difference in./ca,L density between the BRL group and CHF control group (8.3 +/- 1.7 vs. 8.2 +/- 2.6 pA/pF, P > 0.05), which was higher than in the normal control group (6.0 +/- 1.8 pA/pF, P < 0.01). There was no difference in the mRNA expression of alpha(2)delta-2 (Cacna2d2) between the BRL group and CHF control group (0.264 +/- 0.005 vs. 0.243 +/- 0.017, P > 0.05), which was also higher than in the normal control group (0.137 +/- 0.013, P < 0.01). Conclusion beta(3)-Adrenoreceptor stimulation with BRL-37344 was associated with an increase in LA diameter and a decrease in LA function in chronic heart failure. These structural and function changes were not related to I-ca,L or L-type Ca2+ channel alpha(2)delta-2 (Cacna2d2) subunit in the LA myocytes.