Mechanisms underlying enhanced glycogenolysis in livers of 3,5,3'-triiodothyronine-treated rats.
Rats trained on a diurnal controlled meal-feeding schedule and injected with a single dose of 3,5,3'-triiodothyronine (T3) failed to accumulate liver glycogen and incorporated less D-[6-3H]glucose into glycogen than normally observed during the feeding period. In the experimental group, the concentration of liver adenosine 3',5'-cyclic monophosphate (cAMP) did not fall during feeding and the pattern of activities of glycogen phosphorylase, glycogen synthase, and phosphorylase kinase remained conductive to glycogenolysis. Liver lysosomal alpha-glucosidase activity normally fell during feeding periods. After T3 treatment the activities of alpha-glucosidase and two lysosomal cathepsins (B1 and D) were elevated. The evidence suggests that T3 may induce both liver phosphorylase kinase and lysosomal alpha-glucosidase. This outcome of T3 excess, in concert with previously described T3-inducible systems, provides a plausible explanation for the failure of glycogen accumulation in this experimental model.
Nebioglu
S
S
Department of Biochemistry, School of Pharmacy, University of Ankara, Tandogan-Ankara, Turkey.
Wathanaronchai
P
P
Nebioglu
D
D
Pruden
E L
EL
Gibson
D M
DM
D000227:Adenine Nucleotides / Q000378:metabolism; D000818:Animals; D002403:Cathepsins / Q000378:metabolism; D005947:Glucose / Q000378:metabolism; D006006:Glycogen Synthase / Q000378:metabolism; D007700:Kinetics; D008099:Liver / Q000187:drug effects* / Q000378:metabolism; D008112:Liver Glycogen / Q000378:metabolism*; D008247:Lysosomes / Q000201:enzymology; D010764:Phosphorylase Kinase / Q000378:metabolism; D006005:Phosphorylases / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D012016:Reference Values; D014284:Triiodothyronine / Q000494:pharmacology*; D000520:alpha-Glucosidases / Q000378:metabolism
D000227:Adenine Nucleotides; D008112:Liver Glycogen; D014284:Triiodothyronine; D006005:Phosphorylases; D006006:Glycogen Synthase; D010764:Phosphorylase Kinase; D000520:alpha-Glucosidases; D002403:Cathepsins; D005947:Glucose