[Interaction of metal cations with Ca2+-transport sites of the plasma membrane Ca2+ pump of secretory cells of gastric glands].
Investigation of Ca2+ transport by calcium pump of the cell plasma membrane of the gastric glands isolated from guinea pigs and its inhibition by metal cations has been performed. The mainly competitive type of Ca2+ translocation inhibition by the calcium pump by metals cations (0.025-1.00 mM) was determined. Potency of inhibition increases in such an order (I50, mM): Ba2+ (0.336) < Sr2+ (0.251) < Mn2+ (0.099) < Co2+ (0.029) < Cd2+ (0.016). It was shown by one-factor dispersion analysis that potency of inhibition depends on ionic radii and hydration enthalpy of metal cations and also on stability constants of their complexes with oxygen-containing bioligands (acetic, aspartic and glutamic acid) (hx2 = 83.73-85.95). Dependence of the inhibition constants (I50) on ionic radii is most adequately described by the parabolic equation, such a dependence on hydration enthalpy and stability constants with oxygen-containing bioligands--by exponential or multiplicative equations. The conclusion has been made that selective Ca2+ translocation by the calcium pump and its inhibition by metal cations is determined by the interaction between energy of their interaction with cation-binding sites of the transport system and energy of hydration. Energetics of such interactions depends on the steric factors. The physicochemical model of the Ca2+ selective translocation by calcium pump and its inhibition by metal cations has been proposed.
Ivan Franko Lviv National University, Ukraine.
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Dubyts'kyĭ
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Vovkanych
D000818:Animals; D001692:Biological Transport; D002118:Calcium / Q000378:metabolism*; D002413:Cations, Divalent; D005753:Gastric Mucosa / Q000166:cytology / Q000378:metabolism*; D006168:Guinea Pigs; D007700:Kinetics; D008024:Ligands; D008670:Metals / Q000378:metabolism*; D008956:Models, Chemical; D010100:Oxygen / Q000737:chemistry; D013329:Structure-Activity Relationship; D013816:Thermodynamics
D002413:Cations, Divalent; D008024:Ligands; D008670:Metals; D010100:Oxygen; D002118:Calcium