[The effect of tetrandrine on rat myocardial ATPases].
The effect of tetrandrine (Tet) on Na+,K(+)-ATPase and Mg(2+)-ATPase in rat myocardial microsomes was investigated in vitro. Under optimal condition, Tet did not influence Na+,K(+)-ATPase activity but concentration-dependently inhibited Mg(2+)-ATPase with an IC50 of 179 mumol/L. At 10 or 100 mumol/L, Tet caused the concentration-inhibition curves for ouabain a parallel shift to the right. Tet 100 mumol/L markedly increased the activity of Na+,K(+)-ATPase under suboptimal K+ or excessive Ca2+ condition. However, it did not significantly increase the enzyme activity when the Na+ concentration was lower. A kinetic analysis showed that Tet increased the affinity of Na+,K(+)-ATPase to ATP, but did not change the maximal velocity of the enzyme reaction.
Chen
N H
NH
Department of Pharmacology, Nanjing Medical College.
Wang
Y L
YL
Ding
J H
JH
Li
D X
DX
D000470:Alkaloids / Q000494:pharmacology*; D000818:Animals; D044182:Benzylisoquinolines; D017301:Ca(2+) Mg(2+)-ATPase / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D008297:Male; D008861:Microsomes / Q000201:enzymology; D009206:Myocardium / Q000201:enzymology*; D051381:Rats; D011919:Rats, Inbred Strains; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*
D000470:Alkaloids; D044182:Benzylisoquinolines; C009438:tetrandrine; D017301:Ca(2+) Mg(2+)-ATPase; D000254:Sodium-Potassium-Exchanging ATPase