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  • 1
    Electronic Resource
    Electronic Resource
    Alterations in the heart sarcolemmal Ca2+ transport activity by some β-adrenergic antagonists (1984)
    Springer
    Basic research in cardiology 79 (1984), S. 620-626 
    Details
    ISSN: 1435-1803
    Keywords: heart sarcolemma ; Ca2+-stimulated ATPase ; ATP-dependent Ca2+ binding ; β-adrenergic antagonists
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The effects of some β-adrenergic antagonists such as acebutolol, propranolol, pindolol and oxprenolol (1–1000 μM) were studied on the rat heart sarcolemmal Ca2+ transport activities. Pindolol enhanced sarcolemmal ATP-dependent Ca2+ binding and Ca2+-stimulated ATPase whereas acebutolol had no effect. Both propranolol and oxprenolol had biphasic actions on the sarcolemmal Ca2+ pump activities; the lower concentrations (1 and 10 μM) were stimulatory, but the higher concentrations (100 and 1000 μM) were inhibitory. None of the drugs used in this study had any effect on Mg2+ ATPase and non-specific Ca2+ binding activities of heart sarcolemma except that 1000 μM propranolol decreased Mg2+ ATPase activity significantly. Mitochondrial and microsomal ATP-dependent Ca2+ binding activities were unaffected by these drugs (1–1000 μM), except that 1000 μM propranolol was inhibitory. These results suggest differences among various β-adrenergic blocking drugs with respect to their actions on sarcolemmal Ca2+ pump in the myocardium.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01908380
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Differences in sarcolemmal preparations: Cell surface material and membrane sidedness (1983)
    Springer
    Basic research in cardiology 78 (1983), S. 451-461 
    Details
    ISSN: 1435-1803
    Keywords: isolated sarcolemma ; cell surface material ; sialic acid ; membrane sidedness ; sarcolemmal enzymes ; calcium binding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Two different procedures were employed for the isolation of sarcolemma from the rat heart and the membranes were studied with respect to the presence of cell surface material as well as their functional characteristics. Both hypotonic shock-LiBr treatment method (fraction HL) and sucrose density gradient method (fraction S) yielded membranes enriched 8 to 13 fold with respect to Na+−K+ ATPase and adenylate cyclase activites in comparison to heart homogenate. Cell surface material was demonstrated on the outer surface of the vesicles only in fraction HL with cationic dyes, lanthanum and ferritin, applied either to the isolated fractions or perfused in the heart through coronaries. Fraction HL also had high sialic acid content. ATP independent Ca2+ binding in fraction HL was about 6 times more than that in fraction S which had little sialic acid and showed no cell surface staining with cationic dyes. On the other hand, ATP-dependent Ca2+ binding and Ca2+-stimulated Mg2+ dependent ATPase activities in fraction S were 4 to 6 times higher than those in fraction HL. Epinephrine stimulated adenylate cyclase in fractions HL and S by 24 and 3% whereas ouabain was found to inhibit Na+−K+ ATPase in these fractions by 80 and 10% respectively. A mild treatment of the membranes with deoxycholate to eliminate the semipermeable characteristics or effects of sidedness of the vesicles resulted in an almost complete ouabain inhibition of Na+−K+ ATPase in both fractions. These data suggest that presence of cell surface material as well as membrane sidedness has an important role inin vitro expression of functional characteristics of sarcolemma. It is emphasized that sarcolemmal preparations containing cell surface material will provide information more realistic to the native conditionsin situ.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02070168
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
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