Analysis of the inhibitory effect of gypenoside on Na(+), K (+)-ATPase in rats' heart and brain and its kinetics.
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(+).


CONCLUSIONS
Gyp displays its cardiotonic and central inhibitory effects by way of inhibiting heart and brain's microsomal Na(+), K(+)-ATPase activities in rats.
Han
Xiao-yan
XY
Research Center, The Third Affiliated Hospital, Sun Yat-sen University, Guangzhou, 510630, China. hxy3706@126.com
Wei
Hong-bo
HB
Zhang
Fu-cheng
FC
D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D001921:Brain / Q000201:enzymology*; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D029774:Gynostemma; D007700:Kinetics; D008297:Male; D009206:Myocardium / Q000201:enzymology*; D010936:Plant Extracts / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors*
D004791:Enzyme Inhibitors; D010936:Plant Extracts; C474918:gypenoside; D000255:Adenosine Triphosphate; D000254:Sodium-Potassium-Exchanging ATPase