[Effect of inhibitors of energy-dependent Ca2+-transporting systems on calcium pumps of a smooth muscle cell].

Comparative investigation of sensitivity of calcium pumps of sarcolemma, endoplasmic reticulum and mitochondria of the smooth muscle to some inhibitors of energy-dependent Ca(2+)-transporting systems has been carried out in experiments made using the isotope method (45Ca2+) on the fraction of plasmatic membranes and suspension of chemically scanned cells of myometrium as well as on the preparation of highly purified Ca2+, Mg(2+)-ATPase which was solubilized from plasmatic membrane of uterus myocytes. It is proved that the calcium pump of mitochondria is selectively inhibited by ruthenium red (imaginary inhibition constant K, is equal to 0.6 microM); it is nonselectively inhibited by o-vanadate (Ki = 0.6 mM), p-chloromercuribenzoate (Ki = 3.2 microM) and cosine (Ki = 2.1 microM), but is not sensitive to the effect of thapsigargin and cyclopiasonic acid. Mg2+, ATP-dependent calcium pump and transport Ca2+, Mg(2+)-ATPase of plasmatic membrane are nonspecifically inhibited by o-vanadate (the value Ki equals 45.0 and 5.0 microM, respectively) and by cosine (Ki = 0.8 microM in the both cases); this calcium pump is also nonspecifically inhibited by p-chlormercury benzoate (Ki = 3.2 microM), but it is not sensitive to the effect of ruthenium red. Mg2+, ATP-dependent calcium pump of endoplasmic reticulum is selectively inhibited by tapsigargin (Ki = 2.0 nM) and cyclopiasonium acid (Ki = 0.3 microM), but, like calcium pumps of mitochondria and plasma membrane, it is nonspecifically inhibited by o-vanadate (Ki = 45.0 microM); by p-chlormercurybenzoate (Ki = 0.6 microM) and eosin (Ki = 0.8 microM), but it is not sensitive to the effect of ruthenium red. Data that have been obtained can be of use for the further development of the ideas about biochemical regularities of Ca(2+)-dependent control of contraction-relax of the smooth muscles, identifications of energy-dependent calcium pumps of smooth cells and finding out of structure-functional organization of these pumps.