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Early changes of type 2B fibers after denervation of rat EDL skeletal muscle

Early changes of type 2B fibers after denervation of rat EDL skeletal muscle Abstract Skeletal muscle type 2B fibers normally receive a moderate level of motoneuron discharge. As a consequence, we hypothesize that type 2B fiber properties should be less sensitive to the absence of the nerve. Therefore, we have investigated the response of sarcoplasmic reticulum and myofibrillar proteins of type 2B fibers isolated from rat extensor digitorum longus muscle after denervation (2 and 7 days). Single fibers were identified by SDS-PAGE of myosin heavy chain isoforms. Electrophysiological and isometric contractile properties of the whole muscle were also analyzed. The pCa-tension relationship of type 2B single fibers was shifted to the left at 2 days and to right at 7 days after denervation, with significant differences in the Hill coefficients and pCa threshold values in 2- vs. 7-day-denervated fibers. The sarcoplasmic reticulum Ca 2+ uptake capacity and rate significantly decreased after 2 days of denervation, whereas both increased at 7 days. Caffeine sensitivity of sarcoplasmic reticulum Ca 2+ release was transitory and markedly increased in 2-day-denervated fibers. Our results indicate that type 2B fiber functional properties are highly sensitive to the interruption of nerve supply. Moreover, most of 2-day-denervated changes were reverted at 7 days. calcium sensitivity chemically skinned muscle fibers sarcoplasmic reticulum extensor digitorum longus Footnotes The work was supported by grants from Telethon Italy (Grant no. 620 to D. Danieli-Betto and no. 1286 to R. Betto), “Cofinanziamento Italian Ministero dell'Universitá della Ricerca Scientifica e Tecnologica 1998 and 1999” (to M. Midrio and D. Danieli-Betto), and Consiglio Nazionale delle Ricerche institutional funds (to R. Betto). Address for reprint requests and other correspondence: D. Danieli-Betto, Dipartimento di Anatomia e Fisiologia Umana, via Marzolo 3, I-35131 Padova, Italy (E-mail: daniela.danieli@unipd.it ). The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “ advertisement ” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. First published December 21, 2001;10.1152/japplphysiol.00673.2001 Copyright © 2002 the American Physiological Society http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Journal of Applied Physiology The American Physiological Society

Early changes of type 2B fibers after denervation of rat EDL skeletal muscle

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References (62)

Publisher
The American Physiological Society
Copyright
Copyright © 2011 the American Physiological Society
ISSN
8750-7587
eISSN
1522-1601
DOI
10.1152/japplphysiol.00673.2001
pmid
11960956
Publisher site
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Abstract

Abstract Skeletal muscle type 2B fibers normally receive a moderate level of motoneuron discharge. As a consequence, we hypothesize that type 2B fiber properties should be less sensitive to the absence of the nerve. Therefore, we have investigated the response of sarcoplasmic reticulum and myofibrillar proteins of type 2B fibers isolated from rat extensor digitorum longus muscle after denervation (2 and 7 days). Single fibers were identified by SDS-PAGE of myosin heavy chain isoforms. Electrophysiological and isometric contractile properties of the whole muscle were also analyzed. The pCa-tension relationship of type 2B single fibers was shifted to the left at 2 days and to right at 7 days after denervation, with significant differences in the Hill coefficients and pCa threshold values in 2- vs. 7-day-denervated fibers. The sarcoplasmic reticulum Ca 2+ uptake capacity and rate significantly decreased after 2 days of denervation, whereas both increased at 7 days. Caffeine sensitivity of sarcoplasmic reticulum Ca 2+ release was transitory and markedly increased in 2-day-denervated fibers. Our results indicate that type 2B fiber functional properties are highly sensitive to the interruption of nerve supply. Moreover, most of 2-day-denervated changes were reverted at 7 days. calcium sensitivity chemically skinned muscle fibers sarcoplasmic reticulum extensor digitorum longus Footnotes The work was supported by grants from Telethon Italy (Grant no. 620 to D. Danieli-Betto and no. 1286 to R. Betto), “Cofinanziamento Italian Ministero dell'Universitá della Ricerca Scientifica e Tecnologica 1998 and 1999” (to M. Midrio and D. Danieli-Betto), and Consiglio Nazionale delle Ricerche institutional funds (to R. Betto). Address for reprint requests and other correspondence: D. Danieli-Betto, Dipartimento di Anatomia e Fisiologia Umana, via Marzolo 3, I-35131 Padova, Italy (E-mail: daniela.danieli@unipd.it ). The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “ advertisement ” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. First published December 21, 2001;10.1152/japplphysiol.00673.2001 Copyright © 2002 the American Physiological Society

Journal

Journal of Applied Physiology – The American Physiological Society

Published: May 1, 2002

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