TY - JOUR
T1 - Effects of thyroxine on protein turnover in rat skeletal muscle
AU - Flaim, K. E.
AU - Li, J. B.
AU - Jefferson, L. S.
PY - 1978/1/1
Y1 - 1978/1/1
N2 - The effects of thyroxine (T4) on protein turnover in skeletal muscle were studied using normal, thyroidectomized (thyrex), and hypophysectomized (hypox) rats. Thyrex rats had a depressed growth rate that was accompanied by 50% reductions in the levels of RNA and the rate of protein synthesis in gastrocnemius muscle, as determined in the perfused hemicorpus. Protein synthetic efficiency (protein synthesis per unit RNA) was decreased by 18%. Daily treatment of thyrex rats with T4 at different dose levels for up to 16 days led to improved growth rates, elevated RNA concentrations, and increased protein synthesis rates. The primary effect of T4 was to increase the protein synthetic capacity of muscle. Protein degradation, determined in the perfused hemicorpus, and activity of a lysosomal protease, determined in unperfused muscle, were reduced in the thyrex condition. Treatment of thyrex rats with T4 increased protein degradative rates, but not protease activity. Hypox rats, which also exhibited depressed skeletal muscle protein synthesis, responded to T4 and combined T4 and growth hormone with marked improvements in protein synthesis.
AB - The effects of thyroxine (T4) on protein turnover in skeletal muscle were studied using normal, thyroidectomized (thyrex), and hypophysectomized (hypox) rats. Thyrex rats had a depressed growth rate that was accompanied by 50% reductions in the levels of RNA and the rate of protein synthesis in gastrocnemius muscle, as determined in the perfused hemicorpus. Protein synthetic efficiency (protein synthesis per unit RNA) was decreased by 18%. Daily treatment of thyrex rats with T4 at different dose levels for up to 16 days led to improved growth rates, elevated RNA concentrations, and increased protein synthesis rates. The primary effect of T4 was to increase the protein synthetic capacity of muscle. Protein degradation, determined in the perfused hemicorpus, and activity of a lysosomal protease, determined in unperfused muscle, were reduced in the thyrex condition. Treatment of thyrex rats with T4 increased protein degradative rates, but not protease activity. Hypox rats, which also exhibited depressed skeletal muscle protein synthesis, responded to T4 and combined T4 and growth hormone with marked improvements in protein synthesis.
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M3 - Article
C2 - 686169
AN - SCOPUS:0018001263
SN - 0363-6100
VL - 4
SP - E231-E237
JO - American Journal of Physiology Endocrinology Metabolism and Gastrointestinal Physiology
JF - American Journal of Physiology Endocrinology Metabolism and Gastrointestinal Physiology
IS - 2
ER -