| Objectives:To investigate effects of serum containing dioscin on normal sodium current (INa), L-type calcium current (Ica,L) and on abnormal sodium current (INa), L-type calcium current (Ica,L) subjected to hypoxia/reoxygenation and reveal the mechanisms of cardioprotection and antiarrhymias.Methods:Serum was obtained from the aortaventralis from Wistar rats after4days oral administration of dioscin300mg (kg/d),2/day. Single ventricular myocytes were isolated from adult rat hearts by enzymatic dissociation and effects of different dosage dioscin on normal sodium current (Ina), L-type calcium current (Ica,L) and on abnormal sodium current (INa), L-type calcium current (lca,L) induced by hypoxia/reoxygenation were observed with whole-cell patch clamp.Results:1. Serum containing dioscin shifted downward the Ⅰ-Ⅴ curve with increased peak current density. With the effects of1μl,10μl and100μl serum containing dioscin, the peak current density were dose-dependently changed from (-52.10±3.80) pA/pF to (-76.44±4.09) pA/pF and (-81.96±4.70)pA/pF respectively (p＜0.01vs control). Dioscin facilitated the activation process and the recovery process with the inactivation process unchanged.2. In hypoxia/reoxygenation model, the Ⅰ-Ⅴ curve of INa were shifted upward with peak current density decreased from (-52.10±3.80) pA/pF to (-41.16±2.43) pA/pF, which was restored to (-48.71±2.43) pA/pF,(-64.98±2.44) pA/pF,(-69.67±2.44) pA/pF by serum containing dioscin with increased of18.34%,57.87%(p<0.01vs H/R),69.27%(p＜0.01vs H/R) respectively. Hypoxia/reoxygenation group shifted Ina steady-state activation curves and recovery curves to right and inactivation curves to left, which made activate and recover process slowly and inactivate process quickly. Serum containing dioscin restored the right-shifted activation and recovery curves, but had no effects on the inactivation curves.3. Serum containing dioscin shifted upward the Ⅰ-Ⅴ curve with decreased peak current density. With the effects of1μl,10μl and100μl serum containing dioscin, the peak current density was dose-dependently changed from (-3.35±0.50) pA/pF to (-3.31±0.23) pA/pF,(-3.03±0.29) pA/pF and (-2.69±0.75) pA/pF respectively (p<0.01vs control). Dioscin retarded the activation process and recovery process, accelerated the inactivation process.4. In hypoxia/reoxygenation model, the Ⅰ-Ⅴ curve of Ica,L were shifted downward with peak current density increased from (-3.35±0.50) pA/pF to (-5.69±0.25) pA/pF, which was restored to (-5.28±0.18) pA/pF,(-4.41±0.22)pA/pF,(-3.83±0.21)pA/pF by serum containing dioscin by inhibition of7.21%,22.50%(p<0.01vs H/R),32.69%(p<0.01vs H/R). Hypoxia/reoxygenation group turned Ica,L steady-state activation curves and recovery curves to left and inactivation curves to right, which made activation and recovery process quickly and inactivate process slowly. Serum containing dioscin can restore the left-shifed activation and recovery curves, the right-shifted inactivation curves.Conclusions:1. Serum containing dioscin increase the sodium current (Ina) by facilitating the activation process and accelerating the recovery process of sodium channel.2. Hypoxia/reoxygenation decrease peak of INa and shift upward Ⅰ-Ⅴ current inhibited peak current densify.1μl,10μl and100μl serum containing dioscin recover the abnormal sodium current induced by hypoxia/reoxygenation via facilitating the activation process and accelerating the recovery process of sodium channel.3. Serum containing dioscin decrease the L-type calcium current (Ica,L) by inhibiting the activation process and the recovery process and facilitating the inactivation process of L-type calcium channel.4. Hypoxia/reoxygenation increase peak of Ica,L and shift downward Ⅰ-Ⅴ current with activated peak current densify.1μl,10μl and100μl serum containing dioscin recover the abnormal calcium current induced by hypoxia/reoxygenation via inhibiting the activation process and the recovery process and facilitating the inactivation process of L-type calcium channel. |
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