title: Intracellular Ca2+ mobilization activated by extracellular ATP in Ehrlich ascites tumor cells.
abstract: Addition of 0.4-25 microM extracellular ATP results in transient, dose-dependent increases in cytosolic free calcium measured in Ehrlich ascites tumor cells. In cells incubated with 1 mM extracellular Ca2+, ATP induces a triphasic Ca2+ transient: an initial rapid increase (2-3 s), a second, slower phase of increase (60-90 s), and, finally, a gradual return to near resting [Ca2+]i (4-5 min). Several findings demonstrate that the initial, rapid phase of Ca2+ transient results from a mobilization of Ca2+ from a non-mitochondrial intracellular store, while the second, slow phase of increase is produced by enhanced influx of Ca2+ across the plasma membrane. Successive additions of extracellular ATP can elicit repetitive Ca2+ transients if the initially added ATP is removed either through the action of native ecto-ATPase activity or exogenous hexokinase. Other adenine nucleotides, including non-hydrolyzable ATP analogs, neither alter cytosolic [Ca2+] nor antagonize the ATP-induced effects. Conversely, other nucleotide triphosphates (ITP, UTP, and GTP) induce Ca2+ transients which are identical to those produced by ATP. A variety of experimental results indicate that these actions of ATP and other nucleotide triphosphates are not due to a generalized increase in plasma membrane permeability. The results suggest that, in these transformed cells, ATP may act in a manner similar to other Ca2+ mobilizing hormones and growth factors.
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology*; D000634:Aminoquinolines; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002286:Carcinoma, Ehrlich Tumor / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism; D004987:Ethers / Q000494:pharmacology; D005456:Fluorescent Dyes; D015759:Ionomycin; D007700:Kinetics; D014544:Uridine Triphosphate / Q000494:pharmacology
chemical_list: D000634:Aminoquinolines; D004987:Ethers; D005456:Fluorescent Dyes; D015759:Ionomycin; D000255:Adenosine Triphosphate; C035739:Quin2; D002118:Calcium; D014544:Uridine Triphosphate