The Effects of Taurine and Astragalus Membranaceus on Ion Currents and Their Expression in Cardiomyocytes After CVB3 Infection

Abstract

Purpose To investigate the effects of taurine and astragalus membranaceus (AM) on ion currents in cardiomyocytes and their expression in mouse myocardium after Coxsackie virus B3 (CVB3) infection. Material and Methods: Cardiomyocytes from Sprague-Dawley (SD) rats were obtained by retrograde perfusion with collagenase and used for recording current of L-type voltage dependent calcium channel (I ca) and Na+ current (I Na ) by whole cell patch clamp techniques. Cardiomyocytes from neonatal SD rats were prepared by digestion with collagenase and used for recording outward potassium current (Iout) and inward rectifying potassium current (I KI). To set up the in vitro model of VMC, 1∼2 × 105 adult and neonatal rat cells were inoculated to the medium with 200 TCID50 (50% tissue culture infection dose) and 100 TCID50 CVB3 for 2h, respectively. In vivo model of VMC was caused by intraperitoneal injection of 10 TCID50 CVB3 into BALB/c mice. Hearts were removed after 7 days infection and used for examining the expression of L-type voltage dependent Ca2+ channel (LVDCC)α1 subunit and voltage-gate potassium channel (Kv) by immunohistochemistry and in situ hybridization, respectively. 1, 8, 16 mmol/L of taurine and 0.2g/ml of AM were added to the medium of in vitro model. in vivo model, 50 mg/day of taurine was given by mouth and 0.5 ml of AM (2 g/ml) was injected intraperitoneally to the mice per day before sacrificed. Results: 1. the I ca and I out were increased while I KI was decreased after inoculation with CVB3 for 2 hours. However, I Na showed no difference between normal and infected cells. The positive hybridization signals of LVDCCα1 subunit (antigen) and Kv1.2, Kv2.1, Kv4.2 were much reinforced after CVB3 infection. 2. taurine and AM could thwart the enhancement of Ica, Iout and reduction of I KI after virus infection. Besides, they could lessen the increased expression level of LVDCCα1 subunit as well as Kv mRNA. Conclusions: The ion currents and expression of calcium and potassium channels were increased after CVB3 infection. Taurine and AM could exert their beneficial effect on VMC through modulating these changes.