These tools will no longer be maintained as of December 31, 2024. Archived website can be found here. PubMed4Hh GitHub repository can be found here. Contact NLM Customer Service if you have questions.


Pubmed for Handhelds

PUBMED FOR HANDHELDS

Search MEDLINE/PubMed

  • Title: Equilibrium calcium-calcium exchange in cardiac sarcolemmal vesicles.
    Author: Slaughter RS, Sutko JL, Reeves JP.
    Journal: J Biol Chem; 1983 Mar 10; 258(5):3183-90. PubMed ID: 6826557.
    Abstract:
    Ca-Ca isotopic exchange activity in bovine cardiac sarcolemmal vesicles was measured under equilibrium conditions, i.e. where intra- and extravesicular media have identical compositions. The results demonstrate that the monovalent cations K+, Li+, and Rb+ stimulate the process of Ca-Ca exchange. The presence of monovalent cations increases the Vmax for this process but has little effect on the Km for Ca2+. Maximal stimulation of exchange activity occurs when the monovalent cations are present on both sides of the vesicle membrane; a lesser degree of stimulation is observed when the cations are present at only one membrane surface. Na+ also stimulates Ca-Ca exchange at low concentrations (0.5-8 mM) but at high concentrations causes a marked inhibition. The latter effect is due to a competition between Na+ and Ca2+ for a site on the exchange carrier. The presence of monovalent cations alters the pH profile for Ca-Ca exchange. In the absence of stimulating cations, Ca-Ca exchange activity exhibits a maximum at pH 7.0 and then drops to approximately half the peak value at pH 7.5 or higher. In contrast, the rate of Ca-Ca exchange in the presence of monovalent cations continues to increase as the pH is raised from pH 6 to pH 9. Measurements of 86Rb+ fluxes demonstrate that Rb-stimulated Ca-Ca exchange does not involve the co-transport of Rb+. Monovalent cations produce no stimulation of Na-dependent Ca2+ fluxes (Na-Ca exchange) when present on the same side of the membrane as Ca2+. The results are discussed in terms of an extension of the model for the Na-Ca exchanger that was described in the accompanying paper (Reeves, J.P., and Sutko, J.L. (1983) J. Biol. Chem. 258, 3178-3182).
    [Abstract] [Full Text] [Related] [New Search]