Effects of thyroid hormone on fast‐ and slow‐twitch skeletal muscles in young and old rats.

1. The effects of 4 weeks of thyroid hormone treatment on contractile, enzyme‐histochemical and morphometric properties and on the myosin isoform composition were compared in the slow‐twitch soleus and the fast‐twitch extensor digitorum longus (EDL) muscle in young (3‐6 months) and old (20‐24 months) male rats. 2. In the soleus of untreated controls, contraction and half‐relaxation times of the isometric twitch increased by 19‐32% with age. The change in contractile properties was paralleled by an age‐related increase in the proportions of type I fibres and type I myosin heavy chain (MHC) and slow myosin light chain (MLC) isoforms. 3. In the EDL of controls, contraction and half‐relaxation times were significantly prolonged (21‐38%) in the post‐tetanus twitch in the old animals. No significant age‐related changes were observed in enzyme‐histochemical fibre‐type proportions, although the number of fibres expressing both type IIA and IIB MHCs and of fibres expressing slow MLC isoforms was increased in the old animals. 4. Serum 3,5,3',5'‐tetraiodothyronine (T4) levels were lower (34%) in the old animals, but the primary byproduct of T4, 3,5,3'‐triiodothyronine (T3), did not differ between young and old animals. 5. The effects of 4 weeks of thyroid hormone treatment were highly muscle specific, and were more pronounced in soleus than in EDL, irrespective of animal age. In the soleus, this treatment shortened the contraction and half‐relaxation times by 35‐57% and decreased the number of type I fibres by 66‐77% in both young and old animals. In EDL, thyroid hormone treatment significantly shortened the contraction time by 24%, but the change was restricted to the old animals. 6. In conclusion, the ability of skeletal muscle to respond to thyroid hormone treatment was not impaired in old age and the age‐related changes in speed of contraction and enzyme‐histochemical properties and myosin isoform compositions were diminished after thyroid hormone treatment in both the soleus and EDL.

[1]  M. Brooke,et al.  THREE "MYOSIN ADENOSINE TRIPHOSPHATASE" SYSTEMS: THE NATURE OF THEIR pH LABILITY AND SULFHYDRYL DEPENDENCE , 1970, The journal of histochemistry and cytochemistry : official journal of the Histochemistry Society.

[2]  B. Swynghedauw.  Developmental and functional adaptation of contractile proteins in cardiac and skeletal muscles. , 1986, Physiological reviews.

[3]  B. Nadal-Ginard,et al.  All members of the MHC multigene family respond to thyroid hormone in a highly tissue-specific manner. , 1986, Science.

[4]  J. Stull,et al.  Myosin light chain phosphorylation in vertebrate striated muscle: regulation and function. , 1993, The American journal of physiology.

[5]  L. Larsson,et al.  Effects of ageing on enzyme-histochemical, morphometrical and contractile properties of the soleus muscle in the rat , 1989, Journal of the Neurological Sciences.

[6]  D. Walker,et al.  Effects of thyroidectomy on development of skeletal muscle in fetal sheep. , 1991, American Journal of Physiology.

[7]  D. Danieli Betto,et al.  Type 1, 2A, and 2B myosin heavy chain electrophoretic analysis of rat muscle fibers. , 1986, Biochemical and biophysical research communications.

[8]  W. Mommaerts,et al.  Evidence for a direct action of thyroid hormone in specifying muscle properties. , 1982, The American journal of physiology.

[9]  M. Zeviani,et al.  Myofibrillar-protein isoforms and sarcoplasmic-reticulum Ca2+-transport activity of single human muscle fibres. , 1984, The Biochemical journal.

[10]  Simon C Watkins,et al.  Hereditary pituitary dwarfism in mice affects skeletal and cardiac myosin isozyme transitions differently , 1985, The Journal of cell biology.

[11]  K M Baldwin,et al.  Isomyosin distributions in rodent muscles: effects of altered thyroid state. , 1990, Journal of applied physiology.

[12]  L. Gorza.  Identification of a novel type 2 fiber population in mammalian skeletal muscle by combined use of histochemical myosin ATPase and anti-myosin monoclonal antibodies. , 1990, The journal of histochemistry and cytochemistry : official journal of the Histochemistry Society.

[13]  P. Volpe,et al.  Ca2+ release from sarcoplasmic reticulum of skinned fast- and slow-twitch muscle fibers. , 1988, The American journal of physiology.

[14]  D. Pette,et al.  The multiplicity of combinations of myosin light chains and heavy chains in histochemically typed single fibres. Rabbit soleus muscle. , 1987, The Biochemical journal.

[15]  P. D. de Boer,et al.  Distribution of the nuclear thyroid-hormone receptor in extraocular and skeletal muscles. , 1992, The Journal of endocrinology.

[16]  H. Miyata,et al.  Myosin heavy chain isoform transition in ageing fast and slow muscles of the rat. , 1992, Acta physiologica Scandinavica.

[17]  W. Pardridge,et al.  Preferential release of triiodothyronine: an intrathyroidal adaptation to reduced serum thyroxine in aging rats. , 1983, Journal of gerontology.

[18]  V. Laudet,et al.  3,5,3'-Triiodothyronine positively regulates both MyoD1 gene transcription and terminal differentiation in C2 myoblasts. , 1992, Molecular endocrinology.

[19]  N. Rosenthal,et al.  Paired MyoD-binding sites regulate myosin light chain gene expression. , 1991, Proceedings of the National Academy of Sciences of the United States of America.

[20]  T. P. White,et al.  Neuromuscular adaptations to cross-reinnervation in 12- and 29-mo-old Fischer 344 rats. , 1991, The American journal of physiology.

[21]  G. Diffee,et al.  Control of myosin heavy chain expression: interaction of hypothyroidism and hindlimb suspension. , 1991, The American journal of physiology.

[22]  E. Kugelberg,et al.  Transmission and contraction fatigue of rat motor units in relation to succinate dehydrogenase activity of motor unit fibres. , 1979, The Journal of physiology.

[23]  P. D. Gollnick,et al.  Muscular enlargement and number of fibers in skeletal muscles of rats. , 1981, Journal of applied physiology: respiratory, environmental and exercise physiology.

[24]  L. Larsson,et al.  MHC composition and enzyme-histochemical and physiological properties of a novel fast-twitch motor unit type. , 1991, The American journal of physiology.

[25]  L. Larsson,et al.  An age-related type IIB to IIX myosin heavy chain switching in rat skeletal muscle. , 1993, Acta physiologica Scandinavica.

[26]  L. Larsson,et al.  Effects of age on enzyme-histochemical fibre spectra and contractile properties of fast- and slow-twitch skeletal muscles in the rat , 1986, Journal of the Neurological Sciences.