Analysis of the Inhibitory Effect of Gypenoside on Na~+, K~+-ATPase in Rats' Heart and Brain and Its Kinetics

摘要

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 IC_(50) 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.