T. O. Veklich

Palladin Institute of Biochemistry,National Academy of Sciences of Ukraine, Kyiv;
e-mail: veklich@biochem.kiev.ua

Our study on the plasma membrane vesicles and myometrium cells treated with 0.1% digitonin showed that inhibitory effect of calix[4]arene C-90 (5,11,17,23-tetra(trifluoro)methyl(phenylsulphonylimino)-methylamino-25,26,27,28-tetrapropoxy-calix[4]arene) on the plasma membrane Ca²⁺,Mg²⁺-ATPase was more significant than on the Ca²⁺,Mg²⁺-ATPase in sarcoplasmic reticulum (the inhibition coefficient I_0.5 values were 20.2 ± 0.5 µM and 57.0 ± 1.4 µM for the plasma membrane Ca²⁺,Mg²⁺-ATPase and Ca²⁺,Mg²⁺-ATPase in sarcoplasmic reticulum, respectively (n = 5)). Inhibition kinetics of calix[4]arene C-90 effect on the Ca²⁺,Mg²⁺-ATPase activities in plasma membrane and sarcoplasmic reticulum were studied. This substance inhibited both pumps as complete noncompetitive inhibitor. Calix[4]arene C-90 caused the increase of intracellular Ca²⁺ concentration and decrease of hydrodynamic diameter in smooth muscle cells similar to the action of uterotonic drug oxytocin.