T. O. Veklich, O. A. Shkrabak, S. O. Kosterin
Influence of aliphatic polyamines of spermine and spermidine on the enzymatic activity of the ouabain-sensitive Nа+,K+-АТРase and the ouabain-resistant basal Mg2+-АТРase (specific activity?– 10.6?± 0.9 and 18.1 ± 1.2 ?M Рі?/hour on 1?mg of protein accordingly, n = 7) has been studied in the experiments carried out with the suspension of the myometrium cell plasmatic membranes treated with 0.1% digitonin solution. It was found, that the polyamine spermine in concentration of 1?and 10?mM activated the Na+,K+-АТРase by 54 and 64% on the average relative to control value. Spermidine also stimulated the Na+,K+-АТРase activity, however it did it less efficiently than spermine: by 8 and 20% on the average at concentration of 1 and 10 mM, accordingly. Similarly, polyamines had affect on the basal Mg2+-АТРase: spermine in concentration of 1 and 10 mM activated it by 26 and 39% relative to control value; spermidine in concentration of 1 and 10 mM activated it by 10 and 32% relative to control. The magnitudes of the apparent activation constant Ка of spermine were 0.35 ± 0.07 and 0.10?± 0.02 mM for Nа+,K+-АТРase and basal Mg2+-АТРase, accordingly (M?±?m, n = 5). It is supposed, that the obtained experimental data can be useful in the further research of the membrane mechanisms underlying of the cationic exchange in the smooth muscles, in particular, when investigating the role of the plasmatic membrane in providing electromechanical coupling in them, and also in regulation of ionic homeostasis in the smooth muscle cells.
Key words: Nа+,K+-АТРase, Mg2+-АТРase, plasmatic membrane, smooth muscle cells, myometrium, enzymatic hydrolysis of АТР, kinetic properties of АТРase, polyamines.
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