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Objective:To study the effects of gypenoside(Gyp) on the activity of microsomal Na+,K+-ATPase in rat's heart and brain in vitro.Methods:The microsomal Na+,K+-ATPase was prepared from rat's heart and brain by differential centrifugation.The activity of microsomal Na+,K+-ATPase was assayed by colorimetric technique.Enzyme kinetic analysis method was used to analyze the effect of Gyp on the microsomal Na+,K+-ATPase of rats.Results:Gyp reversibly inhibited the brain and heart's microsomal Na+,K+-ATPase in a concentration-dependent manner,and showed a more potent effect on enzyme in the brain.The IC50 of Gyp for the heart and brain were 58.79±8.05 mg/L and 52.07± 6.25 mg/L,respectively.The inhibition was enhanced by lowering the Na+,or K+ concentrations or increasing the ATP concentration.Enzyme kinetic studies indicated that the inhibitory effect of Gyp on the enzyme is like that of competitive antagonist of Na +,the counter-competitive inhibitor for the substrate ATP,and the mixed-type inhibitor for K+.Conclusion:Gyp displays its cardiotonic and central inhibitory effects by way of inhibiting heart and brain's microsomal Na+,K+-ATPase activities in rats.
Objective: To study the effects of gypenoside (Gyp) on the activity of microsomal Na +, K + -ATPase in rat's heart and brain in vitro. Methods: The microsomal Na +, K + -ATPase was prepared from rat's heart and brain by differential centrifugation. activity of microsomal Na +, K + -ATPase was assayed by colorimetric technique. Enzyme kinetic analysis method was used to analyze the effect of Gyp on the microsomal Na +, K + -ATPase of rats. Results: Gyp reversibly inhibited the brain and heart's microsomal Na +, K + -ATPase in a concentration-dependent manner, and showed a more potent effect on enzyme in the brain. The IC50 of Gyp for the heart and brain were 58.79 ± 8.05 mg / L and 52.07 ± 6.25 mg / L, respectively. enhanced by lowering the Na +, or K + concentrations or increasing the ATP concentration. Enzyme kinetic studies indicated that the inhibitory effect of Gyp on the enzyme is like that of competitive antagonist of Na +, the counter-competitive inhibitor for the substrate ATP, and the mixed-type inhibitor for K + .Conclusion: Gyp displays its cardiotonic and central inhibitory effects by way of inhibiting heart and brain's microsomal Na +, K + -ATPase activities in rats.