Sodium channel, sodium pump, and sodium-calcium exchange activities in synaptosomal plasma membrane vesicles.
نویسندگان
چکیده
منابع مشابه
Sodium channel, sodium pump, and sodium-calcium exchange activities in synaptosomal plasma membrane vesicles.
Two mechanisms of Na+ influx have been observed using synaptosomal plasma membrane vesicles purified by density gradient centrifugation from a synaptosomal hypotonic lysate. First, a 5-fold increase in uptake over basal Na+ entry occurs with 50 microM veratridine. The veratridine-dependent Na+ uptake is partially inhibited by 2 microM tetrodotoxin with an apparent time dependency of action (hal...
متن کاملSodium-calcium ion exchange in cardiac membrane vesicles.
Membrane vesicles isolated from rabbit ventricular tissue rapidly accumulated Ca2+ when an outwardly directed Na+ gradient was formed across the vesicle membrane. Vesicles loaded internally with K+ showed only 10% of the Ca2+ uptake activity observed with Na+-loaded vesicles. Dissipation of the Na+ gradient with the monovalent cation exchange ionophores nigericin or narasin caused a rapid decli...
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The ability of mature mammalian spermatozoa to maintain a co-ordinated and forward motility is dependent upon intracellular free Ca2+ being maintained within anarrow concentration range [l]. At the level of the flagellar plasma membrane this could be achieved by two systems: (a) an ATP requiring Ca2’pump; or (b) a Na+/Ca2+ antiporter. Although such plasma membrane Ca2+extrusion mechanisms have ...
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The initial velocity of Ca2+ uptake via the Na-Ca exchange system in cardiac sarcolemmal vesicles is competitively inhibited by extravesicular Na+. The Hill plots for multisite competitive inhibition are nonlinear, exhibiting a limiting slope of 1 at low Na+ concentrations (less than 20 mM) and 1.6-2.0 at higher concentrations. The Ki for Na+ is approximately 16 mM. Thus, the Ca2+ binding site ...
متن کاملSodium Channel and Sodium
Levels of sodium pump and of sodium channels were measured at different stages of membrane purification. Microsomal fractions of normal human muscle have maximal binding capacities for tetrodotoxin of 230 fmol/mg of protein and of 7.4 pmol/mg of protein for ouabain. Dissociation constant for the complexes formed by the tetrodotoxin derivative and by ouabain with their respective receptors were ...
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ژورنال
عنوان ژورنال: Journal of Biological Chemistry
سال: 1982
ISSN: 0021-9258
DOI: 10.1016/s0021-9258(18)33921-8