[Kinetics of passive transport of Ca2+ in vesicles of myometrial sarcolemma].

It has been shown that kinetics of 45Ca2+ yield from vesicular fraction of plasmic membranes of myometrium cells into the medium with 1 mM EGTA complies with the regularities of irreversible reaction of the third order. It is concluded that Ca2+ yield from the vesicules is not reduced to a simple diffusion transmembrane movement of ions, it underlies the interaction between three calcium ions and sarcolemma in the transfer loci. Values of rate constant and initial rate of Ca2+ yield, of the period of half-yield for specimens obtained from the myometrium of pregnant and non-pregnant rabbits were determined. By comparing the values of passive and ATP-dependent transmembrane currents of calcium ions there is analysed the role of the sarcolemma as Ca2+-transporting structure providing for the processes of myometrium contraction and relaxation.