Effect Of Antibody Against The β1-adrenoceptor On Activity Of Potassium Channels In The Mouse Cardiac Myocytes

Background The functions of ion channels are fundamental for the mechanical and electrophysiology of myocardium, especially the potassium channel of the left ventricle, which is important in this process. Since the serum autoantibodies anginst the cardiacβ1-adrenergic receptor was detected from the idiopathic dilated cardiomyopathy(IDCM)in 1990, from then on, the serum autoantibodies anginst the cardiacβ2/β3-adrenergic receptor were detected in the patients with chronic heart failure(CHF).The autoimmune reation may play an inportant role in the proccess of CHF, but it is not clear about the functiones of the antibodies.Objectives To investigate the influence of antibody against-adrenoceptorβ1 (anti-ADRβ1, simulating autoantibody) on potassium channels.Methods Mouse ventricular cardiac myocytes were prepared by enzymatically isolating technique. The whole-cell patch-clamp technique was used to record K+ currents, in which signals were amplified with an HEKA EPC-10 patch clamp amplifier and controlled with Pulse software. The voltage protocol was a 1-s depolarizing pulse from-50 to +50 mV in 10 mV increments and at a holding potential of -60 mV. Cells were perfused with normal bath solution for 10 minutes to stabilize the currents, and then were perfused with anti-ADRβ1 of different concentrations (1/500,1/100 and 1/50) for 5 minutes respectively. Changes of transient outward potassium channel (Ito) and steady state potassium channel (Iss) current intensity and corresponding current-voltage relationships were determined by whole-cell patch-clamp technique.Results (1) The characteristic of outward potassium channel in the mouse ventricular cardiac myocytes:After ChCl instead of NaCl were added in the extracellular fluid, the sodium channel was blocking-up, under this experimental conditions, the activities of the outward potassium channel was also detected. (2) After ChCl instead of NaCl were added in the extracellular fluid, the calcium channel was blocking-up, the activities of the outward potassium channel was also detected. (3)After perfusing cardiac myocytes with anti-ADRβ1 of different concentrations for 5 minutes, current intensity and corresponding current-voltage relationships of Ito were not changed significantly (P>0.05); (4)Compared with current intensity of Iss (4.7±0.24) pA/pF at normal bath solution, Iss (3.6±0.18) pA/pF was decreased at 1/500 concentration of anti-ADRβ1 without statistically significance, however Iss were significantly decreased both at 1/100 (3.5±0.18) pA/pF and 1/50 (3.1±0.15) pA/pF concentrations of anti-ADRβ1, which displayed obviously dose dependent.Conclusion Antibody against-adrenoceptorβ1 inhibit Iss potassium channels of mouse cardiac myocytes without effect on Ito, which may play a role by stimulating ofβi-adrenergic receptors. The results provide experimental basis to investigate the role of autoantibody against-adrenoceptorβ1 in heart failure.