title: [Effect of calixarene-phosphonic acid on Na+, K+-ATPase activity in plasma membranes of the smooth-muscle cells].
abstract: Effect of calix[4]arenes C-97, C-99, C-107, functionalized by fragments of alpha-hydroxy-phosphonic, alpha-aminophosphonic- and methylene-bisphosphonic acid on enzymatic activity of oubaine-sensitive Na+, K+-ATPase and oubaine-resistant basal Mg2+- ATPase (specific activity - 10.6 +/- 0.9 and 18.1 +/- 1.2 micromol Pi/h per 1 mg of protein, respectively; n = 7) was studied in experiments made on the suspension of myometrium cell plasma membranes treated by 0.1% solution of digitonin. It was found that calixarene-phosphonic acids in concentration of 100 microM inhibited enzymatic activity of Na+, K+-ATPase by 86-98% and did not practically affect activity of Mg2+-ATPase. These calixarenes were more efficient than oubaine in suppressing enzymatic activity of the sodium pump: in case of the effect of calixerenes the value of the appearence constant of inhibition I0.5 was < 0.1 microM. Calixarene-methylene-bisphosphonic acid (calixarene C-97; I0.5 =33 +/- 4 microM (n = 6) takes the most efficient inhibitory effect on Na+,K+-ATPase activity among the studied calixarenes. A phenomenon of negative cooperation: the Hill coefficient value etaH =0.1-0.5<1 is characteristic of both the inhibiting effect of calixarenes and oubaine. Reguliarities of calixarenes C-97 effect on enzymatic activity of Na+,K+-ATPase were studied. As it appeared its inhibiting effect cannot be caused by trivial factors - potentially possible binding of Mg ions by it and (or) this substance effect on Mg2+ interaction with ATP4- in the incubation medium. Calixerene C-97 does not also decrease the enzyme affinity for Mg ions or ATP. However this calixerenes decreases the affinity of Na+,K+-ATPase for Na ions (the value of activation constant K(Na+)) from 50 +/- 4 (control) to 76 +/- 6 microM in the control and under the effect of calixerene, respectively). A conclusion is made that calixerene C-97 is highly-efficient (with respect to oubaine) and selective (with respect to lack of its effect on basal Mg2+-ATPase) inhibitor of Na+,K+-ATPase of plasma membrane. In the practical aspect it may be used in concentration of 1-10 microM in biochemical membranology when testing and studying kinetic and catalytic properties of the sodium pump in case of such experimental model, as the plasma membrane fraction.
authors.forename: T O
authors.initials: TO
authors.lastname: Veklich
authors.forename: S O
authors.initials: SO
authors.lastname: Kosterin
authors.forename: R V
authors.initials: RV
authors.lastname: Rodik
authors.forename: S O
authors.initials: SO
authors.lastname: Cherenok
authors.forename: V I
authors.initials: VI
authors.lastname: Boĭko
authors.forename: V I
authors.initials: VI
authors.lastname: Kal'chenko
mesh_terms: D000818:Animals; D047250:Calixarenes / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology; D002462:Cell Membrane / Q000187:drug effects / Q000201:enzymology; D002478:Cells, Cultured; D004791:Enzyme Inhibitors / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology; D005260:Female; D015394:Molecular Structure; D009215:Myometrium / Q000166:cytology / Q000187:drug effects / Q000201:enzymology; D063065:Organophosphonates / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology; D010042:Ouabain / Q000494:pharmacology; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors*
chemical_list: D004791:Enzyme Inhibitors; D063065:Organophosphonates; D047250:Calixarenes; D010042:Ouabain; D000254:Sodium-Potassium-Exchanging ATPase