Calcium sequestering activities of reticulum vesicles from Xenopus laevis oocytes.
Membrane vesicles isolated from Xenopus laevis full-grown stage VI and mature oocytes accumulate 45Ca in the presence of ATP and oxalate. The Ca2+-pumping activity measured in vitro does not appear to be modified during meiotic maturation; it is not affected by the complex Ca2+-calmodulin. Preliminary experiments have shown that the addition of Na+ (30 mM) rapidly discharges accumulated 45Ca into oocyte vesicles indicating that a Na+/Ca2+ exchange system occurs in this membrane fraction. During progesterone-induced maturation, the different intracellular membranes undergo morphological changes. We suggest that intracellular movement of membrane vesicles could be involved in the local regulation of Ca2+ levels.
D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D000252:Calcium-Transporting ATPases / Q000378:metabolism*; D002458:Cell Fractionation; D002462:Cell Membrane / Q000648:ultrastructure; D004591:Electrophoresis, Polyacrylamide Gel; D004721:Endoplasmic Reticulum / Q000648:ultrastructure*; D005260:Female; D007700:Kinetics; D008565:Membrane Proteins / Q000032:analysis; D008970:Molecular Weight; D009865:Oocytes / Q000201:enzymology / Q000648:ultrastructure*; D010766:Phosphorylation; D014981:Xenopus
D008565:Membrane Proteins; D000252:Calcium-Transporting ATPases; D002118:Calcium