Effects of hypothyroidism on myosin isozyme transitions in developing rat muscle.
Hypothyroidism was induced in young rats by methylthiouracil treatment of pregnant mothers from 18 days of gestation to 4 weeks after birth. Electrophoretic analysis of native myosin isozymes revealed a persistence of neonatal and embryonic myosin in developing fast and slow muscles up to at least 28 days after birth. The appearance of adult fast myosin was inhibited in 28-day old animals, however adult slow myosin was found in the soleus muscle. Immunocytochemical results on the soleus demonstrate a cellular heterogeneity in the response to hypothyroidism. About half fibers have a normal complement of slow myosin and do not contain neonatal myosin. Only the remaining fibers contain the large amounts of neonatal myosin demonstrated by electrophoresis.
D000367:Age Factors; D000818:Animals; D004586:Electrophoresis; D007037:Hypothyroidism / Q000201:enzymology*; D007527:Isoenzymes / Q000378:metabolism; D024510:Muscle Development; D009132:Muscles / Q000201:enzymology; D009218:Myosins / Q000378:metabolism*; D051381:Rats
D007527:Isoenzymes; D009218:Myosins