Myosin heavy chain and sarcoplasmic reticulum protein isoforms in
functionally overloaded cat plantaris muscle fibers.
Talmadge, Robert J., Roland R. Roy, Gordon R. Chalmers, and V. Reggie
Edgerton.
Department of Physiological Science and Brain Research Institute,
University of California, Los Angeles, Los Angeles CA, 90095-1527
APStracts 2:0536A, 1995.
To determine if the adaptations in myosin heavy chain (MHC) isoform
expression following functional overload (FO) are accompanied by
commensurate adaptations in protein isoforms responsible for
relaxation (sarcoplasmic reticulum Ca2+ ATPase, SERCA and
phospholamban, PHL) in single muscle fibers, the isoforms of MHC and
SERCA, and the presence or absence of PHL were determined for cat
plantaris fibers 3 months after FO. In control plantaris, the
relative MHC isoform composition was 23% type I, 21% type IIa, and
56% type IIb. FO resulted in a shift toward slower isoforms (33% type
I, 44% type IIa, and 23% type IIb). In the deep region of the
plantaris, the proportions of type I MHC and hybrid MHC fibers
(containing both type I and II MHCs) were 40% and 200% greater in FO
cats, respectively. FO resulted in a 47% increase in the proportion
of fibers containing only the slow SERCA isoform, SERCA2, and a 41%
increase in the proportion of fibers containing PHL. The proportions
of fibers containing type I MHC, SERCA2, and PHL in control and FO
plantaris were linearly correlated. These data show that adaptations
in MHC isoform expression are accompanied by commensurate adaptations
in sarcoplasmic reticulum protein isoforms in single muscle fibers
after FO.
Received 19 May 1995; accepted in final form 27 November 1995.
APS Manuscript Number A518-5.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 8 December 95