[Effect of spermine on kinetic characteristics of ATP-hydrolase systems of the uterus myocyte plasma membranes].

The paper deals with the activation effect of aliphatic polyamine spermine (1 mM) on the enzymatic activity of ouabain-sensitive Na+,K(+)-ATPase and the ouabain-resistant basal Mg(2+)-ATPase in the suspension of the myometrium cell plasma membranes treated with 0.1% digitonin solution. It was found that spermine increased the enzymatic Na+,K(+)-ATPase activity without disrupting of its dome-shaped dependence on the ratio of [Na+]/ [K+] in isotonic condition. The constants of the enzyme activation by Na+ and K+ ions did not vary. Spermine also did not change the character of dependence of Na+,K(+)-ATPase and Mg(2+)-ATPase activity on the concentration of MgCl2 (0.1-2 mM) and on the concentration of ATP (0.05-1 mM). In this case the affinity for the corresponding compounds did not also vary. Thus, the activation by spermine occurred mainly due to enlargment of enzyme "turnover number" according to V(max) increase. It is expected that the obtained experimental data can be important for further investigations of regulation mechanisms of Na+,K(+)-ATPase and Mg(2+)-ATPase activity and also mechanisms of cations exchange control in the smooth muscles.