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The effects of hypothyroidism on glycogen metabolism in rat skeletal muscle were studied using the perfused rat hindlimb preparation. Three weeks after propylthiouracil treatment, serum thyroxine was undetectable and muscle glycogen and Glc-6-P were decreased. Basal and epinephrine-stimulated phosphorylase a and phosphorylase b kinase activities were also significantly reduced, as were epinephrine-stimulated cAMP accumulation and cAMP-dependent protein kinase activity. Conversely, basal and epinephrine-stimulated glycogen synthase I activities were significantly higher while the Ka of the enzyme for Glc-6-P was lower in hypothyroid animals. Propylthiouracil-treated rats also had increased phosphoprotein phosphatase activities towards phosphorylase and glycogen synthase and decreased activity of phosphatase inhibitor 1. beta-Adrenergic receptor binding and basal and epinephrine-stimulated adenylate cyclase activities were reduced in muscle particulate fractions from hypothyroid rats. Administration of triiodothyronine to rats for 3 days after 3 weeks of propylthiouracil treatment restored the altered metabolic parameters to normal. It is proposed that the decreased beta-adrenergic responsiveness of the enzymes of glycogen metabolism in hypothyroid rat skeletal muscle is due to increased activity of phosphoprotein phosphatases and to reduced beta-adrenergic receptors and adenylate cyclase activity.
D T Chu, and
H Shikama, and
B S Khatra, and
J H Exton
July 1989,
The Biochemical journal,
D T Chu, and
H Shikama, and
B S Khatra, and
J H Exton
September 1991,
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D T Chu, and
H Shikama, and
B S Khatra, and
J H Exton
January 1969,
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D T Chu, and
H Shikama, and
B S Khatra, and
J H Exton
June 1980,
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D T Chu, and
H Shikama, and
B S Khatra, and
J H Exton
December 1983,
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D T Chu, and
H Shikama, and
B S Khatra, and
J H Exton
February 1958,
Proceedings of the Society for Experimental Biology and Medicine. Society for Experimental Biology and Medicine (New York, N.Y.),
D T Chu, and
H Shikama, and
B S Khatra, and
J H Exton
September 1979,
The Proceedings of the Nutrition Society,
D T Chu, and
H Shikama, and
B S Khatra, and
J H Exton
January 1974,
Acta physiologica Polonica,
D T Chu, and
H Shikama, and
B S Khatra, and
J H Exton
January 1990,
Advances in experimental medicine and biology,
D T Chu, and
H Shikama, and
B S Khatra, and
J H Exton
January 1978,
Hormone and metabolic research = Hormon- und Stoffwechselforschung = Hormones et metabolisme,
