title: Thyroid hormones control lysosomal enzyme activities in liver and skeletal muscle.
abstract: Because protein degradation in liver and skeletal muscle is increased by thyroid hormones and decreased by thyroidectomy; we investigated the influence of thyroid hormones on the level of lysosomal enzymes. Hypophysectomized rats received daily injections of L-thyroxine or L-triiodothyronine. After 3 days of this regimen, homogenates of liver and skeletal muscle showed a 2- to 3-fold increase in the activities of cathepsin D, cathepsin B, and other lysosomal enzymes including leucine aminopeptidase, acid phosphatase, beta-galactosidase, N-acetylglucosaminidase, and alpha-mannosidase. In liver, this effect reflected increased enzyme activity in the two subcellular fractions that normally contain lysosomes. Titration of cathepsin D with pepstatin indicated that the increase in this activity resulted from an increase in the number of enzyme molecules. These effects occurred with both pharmacologic (thyrotoxic) and physiologic (growth-promoting) doses of thyroid hormones. Liver and skeletal muscle from thyroidectomized rats had approximately 50% of the normal levels of lysosomal enzyme activities. Under these various conditions, heart and kidney, tissues in which protein degradation does not appear to be influenced by thyroid hormones, showed no significant changes in lysosomal hydrolases. Thus, thyroid hormones regulate proteolytic and other lysosomal enzyme activities in those tissues in which these hormones influence protein degradation. Many characteristic features of hyperthyroidism and hypothyroidism may result from changes in levels of lysosomal enzymes.
mesh_terms: D000135:Acid Phosphatase / Q000378:metabolism; D000818:Animals; D002403:Cathepsins / Q000378:metabolism*; D004186:Disaccharidases / Q000378:metabolism; D007668:Kidney / Q000201:enzymology; D007931:Leucyl Aminopeptidase / Q000378:metabolism; D008099:Liver / Q000201:enzymology*; D008247:Lysosomes / Q000201:enzymology*; D008297:Male; D009132:Muscles / Q000201:enzymology*; D009206:Myocardium / Q000201:enzymology; D011506:Proteins / Q000378:metabolism; D051381:Rats; D013963:Thyroid Hormones / Q000494:pharmacology*
chemical_list: D011506:Proteins; D013963:Thyroid Hormones; D000135:Acid Phosphatase; D004186:Disaccharidases; D002403:Cathepsins; D007931:Leucyl Aminopeptidase
references.citation: J Clin Invest. 1943 Sep;22(5):715-20
references.pmid: 16695055
references.citation: Fed Proc. 1965 May-Jun;24:737-44
references.pmid: 14344234
references.citation: J Exp Med. 1965 May 1;121:835-48
references.pmid: 14278233
references.citation: Arch Biochem Biophys. 1962 Feb;96:340-6
references.pmid: 13919612
references.citation: Nature. 1960 Jan 23;185:248
references.pmid: 14422556
references.citation: Proc Natl Acad Sci U S A. 1977 Jan;74(1):54-8
references.pmid: 264694
references.citation: J Bacteriol. 1976 Dec;128(3):776-84
references.pmid: 791931
references.citation: J Lab Clin Med. 1974 Jul;84(1):54-61
references.pmid: 4833843
references.citation: Science. 1972 Apr 21;176(4032):309-10
references.pmid: 5019788
references.citation: Fed Proc. 1974 Apr;33(4):1112-20
references.pmid: 4361908
references.citation: J Cell Biol. 1971 Mar;48(3):473-89
references.pmid: 4322760
references.citation: Biochem J. 1976 Jun 15;156(3):609-17
references.pmid: 182157
references.citation: Biochem Biophys Res Commun. 1972 May 26;47(4):965-70
references.pmid: 4260317
references.citation: J Biol Chem. 1974 Sep 10;249(17):5458-63
references.pmid: 4547200
references.citation: Am J Physiol. 1975 May;228(5):1341-5
references.pmid: 165730
references.citation: J Biol Chem. 1975 Nov 10;250(21):8487-95
references.pmid: 172501
references.citation: Arch Biochem Biophys. 1972 Sep;152(1):166-74
references.pmid: 5072697
references.citation: J Antibiot (Tokyo). 1970 May;23(5):259-62
references.pmid: 4912600
references.citation: Annu Rev Biochem. 1976;45:747-803
references.pmid: 786161
references.citation: Anal Biochem. 1976 Jan;70(1):39-44
references.pmid: 1259154
references.citation: J Biol Chem. 1970 May 10;245(9):2375-83
references.pmid: 5442278
references.citation: Nature. 1970 Mar 14;225(5237):1048-9
references.pmid: 5416471
references.citation: J Biol Chem. 1969 Jun 25;244(12):3303-15
references.pmid: 5792661
references.citation: J Clin Invest. 1974 Feb;53(2):572-81
references.pmid: 11344572