Serum positive for the autoantibody against the β(1)-adrenoceptor from Chinese patients with congestive heart failure decreases I(ss) in mouse cardiac myocytes.

Autoantibodies targeting the β(1)-adrenergic receptor (AAB-β(1)) display agonist-like effects, which may have a pathogenic role in the progression of heart failure. Here, we used the electrophysiological recordings to explore the effects of AAB-β(1)-positive serum from Chinese patients with heart failure on the activity of the peak transient outward potassium current (I(to)) and the end 50 ms steady-state potassium current (I(ss)) in mouse cardiac myocytes. We found that the AAB-β(1)-positive serum had no effect on the activity of I(to), but it produced a decrease in the currents of I(ss). A low concentration of positive serum (1/100) had a small inhibitory effect on I(ss). However, positive serum at 1 : 10, 1 : 20, and 1 : 50 significantly decreased I(ss). The concentration-dependence analysis showed that the EC(50) of AAB-β(1)-positive serum was 1/60.24 and its nH was 2.86. It indicated that the AAB-β(1) could inhibit I(ss) in mouse cardiomyocyte in a concentration-dependent manner.