title: Predicted changes in concentrations of free and bound ATP and ADP during intracellular Ca2+ signaling.
abstract: High Ca2+ concentrations can develop near Ca2+ sources during intracellular signaling and might lead to localized regulation of Ca2+-dependent processes. By shifting the amount of Ca2+ and other cations associated with ATP, local high Ca2+ concentrations might also alter the substrate available for membrane-associated and cytoplasmic enzymes. To study this, simultaneous equations were solved over a range of Ca2+ and Mg2+ concentrations to determine the general effects of Ca2+ on the concentrations of free and Ca2+- and Mg2+-bound forms of ATP. To obtain a more specific picture of the changes that might occur in smooth muscle cells, mathematical models of Ca2+ diffusion and regulation were used to predict the magnitude and time course of near-membrane Ca2+ transients and their effects on the free and bound forms of ATP near the membrane. The results of this work indicate that changes in free Ca2+ concentration over the range of 50 nM-100 microM would result in significant changes in free ATP concentration, MgATP concentration, and the CaATP-to-MgATP concentration ratio.
authors.affiliation: Department of Physiology and Biophysics, University of Calgary, Alberta, Canada.
authors.forename: M E
authors.initials: ME
authors.lastname: Kargacin
authors.forename: G J
authors.initials: GJ
authors.lastname: Kargacin
mesh_terms: D000244:Adenosine Diphosphate / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism*; D000465:Algorithms; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002462:Cell Membrane / Q000201:enzymology; D003198:Computer Simulation; D003593:Cytoplasm / Q000201:enzymology; D007700:Kinetics; D008954:Models, Biological; D009119:Muscle Contraction; D009130:Muscle, Smooth / Q000502:physiology*; D015398:Signal Transduction; D012984:Software
chemical_list: D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D002118:Calcium