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Formation of sarcomeres in developing myotubes: role of mechanical stretch and contractile activation

Formation of sarcomeres in developing myotubes: role of mechanical stretch and contractile... Abstract In a series of experiments, cultured myotubes were exposed to passive stretch or pharmacological agents that block contractile activation. Under these experimental conditions, the formation of Z lines and A bands (morphological structures, resulting from the specific structural alignment of sarcomeric proteins, necessary for contraction) was assessed by immunofluorescence. The addition of an antagonist of the voltage-gated Na + channels tetrodotoxin (TTX) for 2 days in developing rat myotube cultures led to a nearly total absence of Z lines and A bands. When contractile activation was allowed to resume for 2 days, the Z lines and A bands reappeared in a significant way. The appearance of Z lines or A bands could not be inhibited nor facilitated by the application of a uniaxial passive stretch. Electrical stimulation of the cultures increased sarcomere assembly significantly. Antagonists of L-type Ca 2+ channels (verapamil, nifedipine) combined with electrical stimulation led to the absence of Z lines and A bands to the same degree as the TTX treatment. Western blot analysis did not show a major change in the amount of sarcomeric α-actinin nor a shift in myosin heavy chain phenotype as a result of a 2-day passive stretch or TTX treatment. Results of experiments suggest that temporal Ca 2+ transients play an important factor in the assembly and maintenance of sarcomeric structures during muscle fiber development. muscle development Z lines A bands Footnotes This work was possible through the support of the National Center for Medical Rehabilitation Research. Address for reprint requests and other correspondence: P. G. De Deyne, PhD, MPT, Division of Orthopedics, MSTF, Rm. 400, 10 South Pine St., Baltimore, MD 21201 (E-mail: pdedeyne@smail.umaryland.edu ). 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. Copyright © 2000 the American Physiological Society http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png AJP - Cell Physiology The American Physiological Society

Formation of sarcomeres in developing myotubes: role of mechanical stretch and contractile activation

De Deyne, Patrick G.
AJP - Cell Physiology , Volume 279 (6): C1801 – Dec 1, 2000
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Publisher
The American Physiological Society
Copyright
Copyright © 2010 the American Physiological Society
ISSN
0363-6143
eISSN
1522-1563
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Abstract

Abstract In a series of experiments, cultured myotubes were exposed to passive stretch or pharmacological agents that block contractile activation. Under these experimental conditions, the formation of Z lines and A bands (morphological structures, resulting from the specific structural alignment of sarcomeric proteins, necessary for contraction) was assessed by immunofluorescence. The addition of an antagonist of the voltage-gated Na + channels tetrodotoxin (TTX) for 2 days in developing rat myotube cultures led to a nearly total absence of Z lines and A bands. When contractile activation was allowed to resume for 2 days, the Z lines and A bands reappeared in a significant way. The appearance of Z lines or A bands could not be inhibited nor facilitated by the application of a uniaxial passive stretch. Electrical stimulation of the cultures increased sarcomere assembly significantly. Antagonists of L-type Ca 2+ channels (verapamil, nifedipine) combined with electrical stimulation led to the absence of Z lines and A bands to the same degree as the TTX treatment. Western blot analysis did not show a major change in the amount of sarcomeric α-actinin nor a shift in myosin heavy chain phenotype as a result of a 2-day passive stretch or TTX treatment. Results of experiments suggest that temporal Ca 2+ transients play an important factor in the assembly and maintenance of sarcomeric structures during muscle fiber development. muscle development Z lines A bands Footnotes This work was possible through the support of the National Center for Medical Rehabilitation Research. Address for reprint requests and other correspondence: P. G. De Deyne, PhD, MPT, Division of Orthopedics, MSTF, Rm. 400, 10 South Pine St., Baltimore, MD 21201 (E-mail: pdedeyne@smail.umaryland.edu ). 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. Copyright © 2000 the American Physiological Society

Journal

AJP - Cell Physiology – The American Physiological Society

Published: Dec 1, 2000

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