A new affine inhibitor of sodium pump thiacalix[4]arene С-1193 increases the intracellular concentration of Ca ions and modifies myometrium contractility

The methods of enzymatic and kinetic analysis were used to demonstrate that thiacalix[4]arene-bis-hydroxymethylphosphonic acid С-1193 had the inhibitory effect (І0.5 = 42.1 ± 0.6 nM) on Na+,K+-ATPase activity in the plasma membrane of myometrium cells with no effect on the relative activity of other ATPases localized in this subcellular structure. The method of confocal microscopy and Са2+-sensitive fluorescent probe fluo-4 were used to demonstrate that thiacalix[4]arene С-1193 increased the intracellular concentration of Ca ions in the immobilized uterine myocytes. The tenzometric studies proved that С-1193 (10 and 100 μМ) increased the isometric phasic contractions, induced via the paths of both electromechanical (depolarization with high-potassium solution) and pharmacomechanical (application of uterotonic hormone oxytocin, neurotransmitter acetylcholine or selective agonist of muscarinic acetylcholine receptors cevimeline) coupling. Application of thiacalix[4]arene С-1193 as a selective and effective inhibitor of Nа+,K+-ATPase may be useful both for studyng the regulation of ion homeostasis in smooth muscle cells and creation of new uterotonics based on the calixarene core. Keywords: contractility mechanokinetics, myometrium, Na+‚K+-АТРase, thiacalix[4]arene