Abstract: ObjectiveTo observe the effect and mechanism of the antibody against sodium calcium exchanger α-2_(807-820) on cardiac function in Langendorff perfused rat hearts.MethodsSynthesized peptide α-2_(807-820) was used as antigen to immunize the rats.Effects of the antibody against α-2_(807-820) on cardiac function were observed in Langendorff perfused isolated heart.Effect of the antibody on sodium calcium exchanger current was studied using whole cell patch-clamp technique.ResultsThe titer of the antibody increased obviously in α-2_(807-820) immunized rats and the concentration of the purified antibody was 6.3mg/ml.From the results of polyacrylamide gel electrophoresis,only one band with the same molecular weight as standard IgG could be observed in the sample of the purified antibody.The antibody increased left ventricular developed pressure(LVDP)and the maximal rate of LVDP rise/fall(±dp/dt_max)in Langendorff perfused isolated hearts at 10 and 40 nmol/L,and these effects could be largely reversed by KB-R7943.The antibody of 40 nmol/L augmented both outward and inward sodium calcium exchange currents from 1.05±0.17,0.86±0.21 pA/pF to 1.53±0.28,1.23±0.31 pA/pF(P<0.05),respectively.ConclusionThe antibody against α-2_(807-820) could not only strengthen cardiac contraction,but also accelerate its relaxation via enhancement of sodium calcium exchange activity.