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Journal archive > 2006 > N 6 November-December

THE СALIXARENES С-97 AND С-107 STIMULATE INFLUENCE OF OUABAIN
ON THE Na+,K+-АТРase ACTIVITY IN PLASMATIC MEMBRANE OF SMOOTH MUSCLE CELLS

T. O. Veklich1, O. A. Shkrabak1, S. O. Kosterin1, R. V. Rodik2, S. O. Cherenok2, V. I. Boyko2, V. I. Kalchenko2

1Palladin Institute of Biochemistry, National Academy of Sciences of Ukraine, Kyiv;
2Institute of Organic Chemistry, National Academy of Sciences of Ukraine, Kyiv;
е-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.; This email address is being protected from spambots. You need JavaScript enabled to view it.

In the experiments carried out with the suspension of the myometrium cell plasmatic membranes treated with 0.1% digitonin solution the authors investigated influence of the сalix[4]arenes С-97 and С-107 (codes are shown) on ouabain effect on the Nа+,K+-АТРase activity. It was shown that calixarenes in concentration 100 ?M inhibited by 97–98% the enzymatic Na+,K+-АТРase activity, while they did not practically influence on the basal Mg2+-АТРase activity, and suppressed much more effective than ouabain the sodium pump enzymatic activity: in the case of the action of the calixarenes the value of the apparent constant of inhibition I0.5 was <0.1 ?M while for ouabain it was 15–25 ?M. The negative cooperative effect was typical of the inhibitory action of сalixarenes, as well as ouabain: the value of Hills factor nH?=?0.3–0.5 <1. The modelling compound М-3 (0.1 ?M?– 4??M) – a fragment of the calixarene С-107 – did not practically influence the enzymatic activities as Na+,K+-АТРase and basal Mg2+-АТРаse. Hence the influence of calixarene С-107 on the Na+, K+-АТРаse activity is caused by cooperative action of two fragments М-3 and effect of calixarene bowl, rather than by simple action of the fragment М-3. Calixarenes С-97 and С-107, used in concentration corresponding to values of I0.5 (40 and 60?nM, accordingly), essentially stimulated inhibiting action of ouabain on the specific Na+, K+-АТРаse activity in the memrane fraction. Under coaction of ouabain with calixarene С-97 or С-107 there was no additive effect of the action of these inhibitors on the Nа+,K+-АТРase activity. Calixarene С-97 brought in the incubation medium in concentration of 10 nM not only led to inhibition of the Na+,K+-АТРase activity relative to control, but also simultaneously increased the affinity of the enzyme for the cardiac glycoside: the magnitudes of the apparent constant of inhibition I0.5 were 21.0?± 5.2 ?M and 5.3 ± 0.7 ?M. It is concluded, that highly effective inhibitors of the Na+,K+-АТРase activity – сalixarenes С-97 and С-107 can enhance the effect of the sodium pump conventional inhibitor – ouabain, increasing the affinity of the enzyme for the cardiac glycoside (on the example of calixarene С-97).

Key words: Na+,K+-ATPase, Mg2+-ATPase, plasma membrane, smooth muscle cells, myometrium, enzymatic hydrolysis of ATP, kinetic properties of ATPase, calixarenes, complexones, methylene-bis-phosphonic acid, aminophosphonic acid, hydroxyphosphonic acid.

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