[ATP-dependent Ca2+-uptake by the plasma membrane fraction of the myometrium].
The specific activities of Mg2+, Ca2+-ATPase in the plasma membrane fraction of rabbit and cattle myometrium are 8.30 +/- 0.80 and 2.36 +/- 0.48 mkmoles of Pi per mg of protein, respectively. This fraction possesses a higher (in comparison with other subcellular fractions) capacity for ATP-dependent uptake of 45Ca2+ (9.37 +/- 1.66 and 6.86 +/- 0.96 nmoles of 45Ca2+ per mg of protein in 15 min for rabbit and cattle myometrium, respectively); the ratio of ATP-dependent uptake of Ca2+ to adsorbed Ca2+ is also high. Phosphate increases Ca2+ uptake in the presence of ATP and Mg2+. The ionophore A-23187 added to the incubation mixture without ATP and Mg2+ sharply increases Ca2+ binding. An addition of the ionophore at the 15th min of the ATP-dependent Ca2+ uptake causes a complete and rapid release of the accumulated Ca2+. The release of Ca2+ can be also caused by an addition of Na-DS or EGTA to the incubation mixture. This suggests that Ca2+ is accumulated through the plasma membrane inside the closed structures. It was assumed that myometrial sarcolemma plays an essential role in regulation of intracellular Ca2+ concentration in the uterus at rest and that the active Ca2+ efflux from the cells is controlled by the Mg2+, Ca2+-ATPase system.
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001693:Biological Transport, Active; D017301:Ca(2+) Mg(2+)-ATPase; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000378:metabolism*; D002417:Cattle; D002462:Cell Membrane / Q000201:enzymology; D005260:Female; D007700:Kinetics; D009215:Myometrium / Q000201:enzymology*; D011817:Rabbits; D014599:Uterus / Q000201:enzymology*
D000001:Calcimycin; D000255:Adenosine Triphosphate; D017301:Ca(2+) Mg(2+)-ATPase; D000252:Calcium-Transporting ATPases; D002118:Calcium
ATP-zavisimoe nakoplenie Ca2+ fraktsieĭ plazmaticheskikh membran miometriia.