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  • 1
    Electronic Resource
    Electronic Resource
    Regulation of L- and N-types of Ca2+ channels by intracellular ATP4– in frog dorsal root ganglion neurons (1999)
    Springer
    Pflügers Archiv 438 (1999), S. 117-124 
    Details
    ISSN: 1432-2013
    Keywords: Key words ATP ; Dorsal root ganglion neurons ; L-type Ca2+ channel ; N-type Ca2+ channel
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The roles of free Mg2+ ions, ATP4– ions and Mg-ATP complexes in the regulation of N- and L-types of Ca2+ channels were studied in frog dorsal root ganglion (DRG) neurons using the whole-cell patch-clamp technique. Because Mg2+ ions interact with ATP4– ions to form Mg-ATP complexes, addition of one species can influence the concentrations of the other two. In this study their concentrations were carefully controlled by varying the concentrations of two constituents at a time while keeping the third constant. The effects of each of the three species on barium currents through L-type (I BaL) and N-type (I BaN) Ca2+ channels were plotted against its concentrations. The dose-response curves for ATP4– show that I BaL and I BaN proportionally increased with ATP4– concentrations up to 1 mM at three different Mg2+ concentrations. At a fixed concentration of ATP4–, I BaL and I BaN remained unchanged even when pMg changed from 3 to 5. Dose-response curves for I BaL and I BaN plotted against Mg-ATP concentration did not show a consistent pattern. H-7 and Mg2+ ions did not exert any blocking effect on the activity of either Ca2+ channel type, and neither dibutyryl-cAMP nor NKH-477 had any stimulating effect, suggesting that phosphorylation is not likely to be involved in ATP-induced potentiation. From these observations, it is concluded that L-type and N-type Ca2+ channels in frog DRG neurons are regulated by ATP4– ions alone, and that the neuronal Ca2+ channels are regulated by mechanisms that are different from those regulating the cardiac Ca2+ channels.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004240050888
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  • 2
    Electronic Resource
    Electronic Resource
    Effect of sulfhydryl reagents on the regulatory system of the L-type Ca channel in frog ventricular myocytes (2000)
    Springer
    Pflügers Archiv 440 (2000), S. 207-215 
    Details
    ISSN: 1432-2013
    Keywords: Cysteine Frog ventricle L-type Ca channel Sulfhydryl reagents
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract. The effects of sulfhydryl (SH) reagents on the L-type Ca current (I Ca) were studied in frog ventricular myocytes using the whole-cell patch-clamp method. Methanethiosulfonate ethylammonium (MTSEA+) was found to enter the cell through the membrane and cause a remarkable increase in I Ca from the intracellular side. Methanethiosulfonate ethyltrimethylammonium (MTSET+) and methanethiosulfonate ethylsulfonate (MTSES–) could not penetrate the membrane and were effective only when directly applied to the intracellular side. In addition, suppressive effects on I Ca of these MTS reagents were indicated by the following observation. A progressive decay in the peak amplitude of I Ca after establishing maximal I Ca, stimulated by intracellular MTSET+, was prevented by adding extracellular dithiothreitol (DTT). The SH-oxidizing agents N-ethylmaleimide (NEM), chloramine-T (CL-T), 2,2′-dithiodipyridine (DTDP) and 2,2′-dithio-bis-5-nitropyridine (DTBNP) also exerted a stimulatory effect on I Ca. The effect of SH reagents persisted even when cAMP production was inhibited with Rp-cAMP-S, or when G-protein was inhibited with 1 mM GDPβS, indicating that the effect is not due to cAMP production or G-protein stimulation. It is concluded that there are sites on the Ca channels that are subject to direct modification by SH reagents.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004249900242
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
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