Characterization of a (Ca2+ + Mg2+)-ATPase system in the osteoblast plasma membrane.
A high affinity, calmodulin-sensitive (Ca2 + Mg2+)-ATPase was demonstrated in the plasma membrane preparation of three different osteosarcoma cell lines previously demonstrated to respond to parathyroid hormone with an increase in cytosolic calcium and a decrease in pH. The maximal velocity of the enzyme activity in the membrane preparations ranged from 0.83 to 2.42 nmol Pi released per min per mg protein with half-saturation constants of 26 nM of free Ca. The enzyme activity was not affected by Na+, K+, ouabain and azide, and exhibited an absolute requirement for Mg2+ ions. These results suggest a possible role for a membrane Ca2 + Mg2+-ATPase in initiating and perpetuating the ionic control of osteoblastic function.
Shen
V
V
Division of Bone and Mineral Disease, Washington University School of Medicine, St. Louis, MO.
Hruska
K
K
Avioli
L V
LV
D000818:Animals; D017301:Ca(2+) Mg(2+)-ATPase / Q000032:analysis*; D000252:Calcium-Transporting ATPases / Q000032:analysis*; D002460:Cell Line; D002462:Cell Membrane / Q000201:enzymology*; D006801:Humans; D010006:Osteoblasts / Q000201:enzymology*; D012516:Osteosarcoma / Q000378:metabolism; D051381:Rats
D017301:Ca(2+) Mg(2+)-ATPase; D000252:Calcium-Transporting ATPases