[Change in concentration of cytosolic Ca2+ caused by extracellular ATP and ecto-ATP-ase activity in thymocytes and transformed MT-4 cells].
The comparative study of extracellular ATP (ATP0) effect on free cytosolic calcium concentration ([Ca2+]i) in normal (isolated rat thymocytes) and transformed (leukosis MT-4 line) T-cells was carried out. Addition of 1 mM ATP to Ca-free incubation medium of both types of cells, loaded with indo-1, had no effect on [Ca2+]i level. Upon subsequent addition of 1 mM CaCl2 to the incubation medium the rapid and significant increase of [Ca2+]i in MT-4 cells was registered. This effect was maintained within 10 min and was not inhibited by phospholipase C inhibitor 0.2 mM neomycin, that was induced by cation entry into the cells from the extracellular medium. Both types of cells were shown to demonstrate ecto-ATPase activity in the presence of 1 mM MgCl2 or CaC12 in the incubation medium. Estimation of kinetic parameters has indicated that the maximum rate of extracellular ATP hydrolysis by MT-4 cells is higher and Mg2+ and Ca2+ activation constants are lower as compared to respective parameters of ATP hydrolysis by thymocytes. The possible functional significance of the increased level of ecto-ATPase activity in malignantly transformed cells is discussed.
Hrebinyk
S M
SM
Artemenko
O Iu
OIu
Hryniuk
I I
II
Perepelitsyna
O M
OM
Matyshevs'ka
O P
OP
D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D018929:Cell Culture Techniques; D002461:Cell Line, Transformed; D002471:Cell Transformation, Neoplastic / Q000378:metabolism*; D003470:Culture Media; D003600:Cytosol / Q000201:enzymology / Q000378:metabolism*; D005110:Extracellular Space / Q000201:enzymology / Q000378:metabolism*; D005260:Female; D007700:Kinetics; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D013950:Thymus Gland / Q000166:cytology / Q000201:enzymology / Q000378:metabolism*
D003470:Culture Media; D000251:Adenosine Triphosphatases; C027201:ectoATPase; D002118:Calcium