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Effects of Caffeine on Crayfish Muscle Fibers : II. Refractoriness and factors influencing recovery (repriming) of contractile responses

When caffeine evokes a contraction, and only then, crayfish muscle fibers become refractory to a second challenge with caffeine for up to 20 min in the standard saline (5 mM K(o)). However, the fibers still respond with contraction to an increase in K(o), though with diminished tension. Addition of...

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Autores principales: Chiarandini, Dante J., Reuben, John P., Girardier, Lucien, Katz, George M., Grundfest, Harry
Formato: Texto
Lenguaje:English
Publicado: The Rockefeller University Press 1970
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2203014/
https://www.ncbi.nlm.nih.gov/pubmed/5443469
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author Chiarandini, Dante J.
Reuben, John P.
Girardier, Lucien
Katz, George M.
Grundfest, Harry
author_facet Chiarandini, Dante J.
Reuben, John P.
Girardier, Lucien
Katz, George M.
Grundfest, Harry
author_sort Chiarandini, Dante J.
collection PubMed
description When caffeine evokes a contraction, and only then, crayfish muscle fibers become refractory to a second challenge with caffeine for up to 20 min in the standard saline (5 mM K(o)). However, the fibers still respond with contraction to an increase in K(o), though with diminished tension. Addition of Mn slows recovery, but the latter is greatly accelerated during exposure of the fiber to high K(o), or after a brief challenge with high K(o). Neither the depolarization induced by the K, nor the repolarization after its removal accounts for the acceleration, which occurs only if the challenge with K had itself activated the contractile system; acceleration is blocked when contractile responses to K are blocked by reducing the Ca in the bath or by adding Mn. Recovery is accelerated by redistribution of intracellular Cl and by trains of intracellularly applied depolarizing pulses, but not by hyperpolarization. The findings indicate that two sources of Ca can be mobilized to activate the contractile system. Caffeine mobilizes principally the Ca store of the SR. Depolarizations that are induced by high K(o), by transient efflux of Cl, or by intracellularly applied currents mobilize another source of Ca which is strongly dependent upon the entry of Ca from the bathing medium. The sequestering mechanism of the SR apparently can utilize this second source of Ca to replenish its own store so as to accelerate recovery of responsiveness to a new challenge with caffeine.
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spelling pubmed-22030142008-04-23 Effects of Caffeine on Crayfish Muscle Fibers : II. Refractoriness and factors influencing recovery (repriming) of contractile responses Chiarandini, Dante J. Reuben, John P. Girardier, Lucien Katz, George M. Grundfest, Harry J Gen Physiol Article When caffeine evokes a contraction, and only then, crayfish muscle fibers become refractory to a second challenge with caffeine for up to 20 min in the standard saline (5 mM K(o)). However, the fibers still respond with contraction to an increase in K(o), though with diminished tension. Addition of Mn slows recovery, but the latter is greatly accelerated during exposure of the fiber to high K(o), or after a brief challenge with high K(o). Neither the depolarization induced by the K, nor the repolarization after its removal accounts for the acceleration, which occurs only if the challenge with K had itself activated the contractile system; acceleration is blocked when contractile responses to K are blocked by reducing the Ca in the bath or by adding Mn. Recovery is accelerated by redistribution of intracellular Cl and by trains of intracellularly applied depolarizing pulses, but not by hyperpolarization. The findings indicate that two sources of Ca can be mobilized to activate the contractile system. Caffeine mobilizes principally the Ca store of the SR. Depolarizations that are induced by high K(o), by transient efflux of Cl, or by intracellularly applied currents mobilize another source of Ca which is strongly dependent upon the entry of Ca from the bathing medium. The sequestering mechanism of the SR apparently can utilize this second source of Ca to replenish its own store so as to accelerate recovery of responsiveness to a new challenge with caffeine. The Rockefeller University Press 1970-05-01 /pmc/articles/PMC2203014/ /pubmed/5443469 Text en Copyright © 1970 by The Rockefeller University Press This article is distributed under the terms of an Attribution–Noncommercial–Share Alike–No Mirror Sites license for the first six months after the publication date (see http://www.rupress.org/terms). After six months it is available under a Creative Commons License (Attribution–Noncommercial–Share Alike 4.0 Unported license, as described at http://creativecommons.org/licenses/by-nc-sa/4.0/).
spellingShingle Article
Chiarandini, Dante J.
Reuben, John P.
Girardier, Lucien
Katz, George M.
Grundfest, Harry
Effects of Caffeine on Crayfish Muscle Fibers : II. Refractoriness and factors influencing recovery (repriming) of contractile responses
title Effects of Caffeine on Crayfish Muscle Fibers : II. Refractoriness and factors influencing recovery (repriming) of contractile responses
title_full Effects of Caffeine on Crayfish Muscle Fibers : II. Refractoriness and factors influencing recovery (repriming) of contractile responses
title_fullStr Effects of Caffeine on Crayfish Muscle Fibers : II. Refractoriness and factors influencing recovery (repriming) of contractile responses
title_full_unstemmed Effects of Caffeine on Crayfish Muscle Fibers : II. Refractoriness and factors influencing recovery (repriming) of contractile responses
title_short Effects of Caffeine on Crayfish Muscle Fibers : II. Refractoriness and factors influencing recovery (repriming) of contractile responses
title_sort effects of caffeine on crayfish muscle fibers : ii. refractoriness and factors influencing recovery (repriming) of contractile responses
topic Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2203014/
https://www.ncbi.nlm.nih.gov/pubmed/5443469
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