Thiacalix[4]arene С-1087 is the selective inhibitor of the calcium pump of smooth muscle cells plasma membrane

The enzymatic and kinetic analyses were used to demonstrate that 5,11,17,23-tetra(trifluoro)methyl(phenylsulfonylimino)methylamino-25,27-dihexyloxy-26,28-dihydroxythiacalix[4]arene С-1087 effectively inhibited the Са2+,Mg2+-АТРase activity of the rat myometrium cells plasma membrane (І0.5 = 9.4 ± 0.6 µM) with no effect on the relative activity of other membrane ATPases. With the use of confocal microscopy and Ca2+-sensitive fluorescent probe fluo-4, it was shown that the application of thiacalix[4]arene С-1087 to the immobilized uterus myocytes increased the cytosolic concentration of Ca2+. Tenzometric studies of rat uterus smooth muscles with the subsequent mechanokinetic analysis revealed that thiacalix[4]arene С-1087 considerably decreased the maximal velocity of the relaxation of both spontaneous contractile response and contraction induced by hyperpotassium solution. Keywords: contraction-relaxation mechanokinetics, cytosolic Ca(2+), myometrium, plasma membrane Са(2+)‚Mg(2+)-АТРase, smooth muscle cell, thiacalix[4]arene