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Postnatal histochemical fiber type differentiation in normal and hypothyroid rat soleus muscle
Author(s) -
Sugie Hideo,
Verity M. Anthony
Publication year - 1985
Publication title -
muscle and nerve
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.025
H-Index - 145
eISSN - 1097-4598
pISSN - 0148-639X
DOI - 10.1002/mus.880080805
Subject(s) - endocrinology , fiber type , medicine , soleus muscle , propylthiouracil , myosin , chemistry , adenosine triphosphatase , myosin atpase , fiber , atpase , biology , anatomy , skeletal muscle , biochemistry , hormone , enzyme , organic chemistry
We have analyzed the effect of 6‐propylthiouracil‐induced hypothyroidism on neonatal fiber type differentiation in the rat soleus muscle. Body weight, total soleus fiber number, histochemical fiber type differentiation, and morphometry were determined at 7, 14, 21, and 28 days. Neonatal hypothyroidism (1) inhibits the apparent ∼50% increase in soleus muscle fiber number occurring at 14–21 days, (2) blocks the transformation of type 2C to type 2A fibers occurring between 14 and 21 days, (3) preferentially inhibits the increase in type 2 fiber diameter, and (4) retards the development of sarcoplasmic reticulum. Immature muscle fibers reveal type 1 and type 2 fiber myosin adenosine triphosphatase (ATPase) differentiation at pH 10.3, which drops to pH 9.4 with maturation. No myosin ATPase differentiation was found at pH 9.4 in the hypothyroid animals, even at 28 days.