Т. O. Veklich1, N. S. Kocheshkova2, R. V. Rodik3, V. I. Boyko3, Z. D. Vorobets2, S. O. Kosterin1
The paper is devoted to comparative analysis of the influence of a new class of macrocyclic compounds – calixarens on enzymatic activity of two ATP-hydrolase systems localized in the plasmatic membrane of contractile (myocytes of the uterus) and mobile (spermatozoids) cells?– Na+,K+-ATPase and basal Mg2+-АТРase. The experiments performed on plasmatic membrane suspensions of myometrium and spermatozoids treated with detergent the authors studied the influence of calixarens C-97, C-99, C-107 (identified by the codes), functionalized with fragments of alpha-hydroxyphosphonic, alpha-aminophosphonic and methylenbisphosphonic acids accordingly, on enzymatic activity. The results have shown that C-97 and C-107 calixarenphosphonic acids in 100 µM concentration (97–99%) inhibit Na+,K+-ATPase activity in both cases almost completely. C-99 (100?µM) calixaren appeared to be less effective with regard of its influence on the enzymatic systems under study: in the case of plasmatic membranes of myometrium suspension the activity of Na+,K+-АТРase was decreased by 84–88%, and in the case of spermatozoids suspension?– just by 15–20% of the control. All the studied calixarens (for both objects) in the maximal concentration (100 µM) practically did not influence the activity of basal Mg2+-ATPase. The calixarens inhibited the enzymatic activity of Na+,K+-ATPase more effectively than ouabain: in the first case the value of apparent inhibition constant I0,5 was 25–100 nM, and in the second case – 20–100 µM. The inhibition influence of calixarens on Na+,K+-AТРase activity is characterized by the phenomenon of negative cooperativity (Hill’s coefficient nH < 1); the influence of ouabain in the case of plasmatic membranes of myometrium suspension is also characterized by negative cooperativity (nH?< 1), and in case of spermatozoids suspension?– by positive cooperativity (nH > 1). The above results show that the studied calixarens are effective inhibitors of Na+,K+-ATPase plasmatic membrane of contractive and mobile cells (C-97, C-99, C-107 calixarens in case of myocytes of uterus, and C-97, C-107 calixarens in case of spermatozoids).
Key words: Na+,K+-ATPase, Mg2+-ATPase, plasma membrane, retractiveness (mobility), myometrium, smooth muscle cells, spermatozoids, ouabain, calixarens.
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