Studies on the decrease of liver cytochrome P-450 content by triiodothyronine.
In the rat liver, the microsomal content of cytochrome P-450 decreased by 50% after triiodothyronine (T3) administration. The molecular basis for the decreased cytochrome P-450 levels was investigated. The activities of the enzymes involved in heme synthesis or degradation were not altered by thyroid hormone administration. The incorporation of 3H-delta-aminolaevulinate into the liver microsomal heme was markedly reduced in T3-treated rats. The latter appeared not to reflect a lowered binding affinity of the apoprotein moiety of cytochrome P-450 for heme. The sodium dodecyl sulfate gel electrophoresis of the microsomal preparation showed a decrease in apocytochrome P-450. It is suggested that the amount of the apocytochrome may be the primary event affected in the formation of cytochrome P-450, by triiodothyronine treatment of thyroidectomized rats.
Kleiman de Pisarev
D L
DL
Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Argentina.
Ferramola de Sancovich
A M
AM
Sancovich
H A
HA
D000624:5-Aminolevulinate Synthetase / Q000378:metabolism; D000622:Aminolevulinic Acid / Q000378:metabolism; D000818:Animals; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D006418:Heme / Q000378:metabolism; D006801:Humans; D011163:Hydroxymethylbilane Synthase / Q000378:metabolism; D008297:Male; D008862:Microsomes, Liver / Q000187:drug effects / Q000201:enzymology*; D000623:Porphobilinogen Synthase / Q000378:metabolism; D011506:Proteins / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D012709:Serum Albumin / Q000378:metabolism; D014284:Triiodothyronine / Q000494:pharmacology*
D011506:Proteins; D012709:Serum Albumin; D014284:Triiodothyronine; D006418:Heme; D000622:Aminolevulinic Acid; D003577:Cytochrome P-450 Enzyme System; D000624:5-Aminolevulinate Synthetase; D011163:Hydroxymethylbilane Synthase; D000623:Porphobilinogen Synthase