ISSN:
1432-1424
Keywords:
Key words: Ca2+ channels — DHP receptors — Upregulation — Skeletal muscle — Channel blockers
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Chemistry and Pharmacology
Notes:
Abstract. The effects of a long-term blockade of L-type Ca2+ channels on membrane currents and on the number of dihydropyridine binding sites were investigated in skeletal muscle fibers. Ca2+ currents (I Ca) and intramembrane charge movement were monitored using a voltage-clamp technique. The peak amplitude of I Ca increased by more than 40% in fibers that were previously incubated for 24 hr in solutions containing the organic Ca2+ channel blocker nifedipine or in Ca2+-free conditions. A similar incubation period with Cd2+, an inorganic blocker, produced a moderate increase of 20% in peak I Ca. The maximum mobilized charge (Q max) increased by 50% in fibers preincubated in Ca2+-free solutions or in the presence of Cd2+. Microsomal preparations from frog skeletal muscle were isolated by differential centrifugation. Preincubation with Cd2+ prior to the isolation of the microsomal fraction doubled the number of 3H-PN200-110 binding sites and produced a similar increase in the values of the dissociation constant. The increase in the number of binding sites is consistent with the increase in the peak amplitude of I Ca as well as with the increase in Q max.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/s002329900504
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