Modulation by glycerol of hepatic glycero-3-phosphate concentration, ketogenesis, and output of triglyceride and glucose in perfused livers from hyperthyroid and euthyroid rats.
Decreased glycero-3-phosphate (glycero-3-P) concentration, decreased output of triglyceride and glucose, increased output of apolipoprotein A-I, and increased ketogenesis were observed with isolated perfused livers from triiodothyronine-treated rats in comparison to livers from euthyroid animals. Infusion of glycerol produced a concentration-dependent accumulation of glycero-3-P in perfused livers from hyperthyroid and euthyroid rats, which was considerably enhanced in the euthyroid group. The antiketogenic effect of glycerol in livers from triiodothyronine-treated rats was accompanied by increased output of glucose and triglyceride, while no change in the output of apolipoprotein A-I was observed. The reduction of ketogenesis (49%) in euthyroid livers by glycerol was not accompanied by increased triglyceride output, while with the largest amount of glycerol infused, decreased output of apolipoprotein A-I was seen. Output of triglycerides by livers from hyperthyroid rats correlated with hepatic concentration of glycero-3-P and was maximal at a glycero-3-P concentration (0.5 mumol/g), similar to that observed in livers from euthyroid rats in the absence of glycerol. Availability of glycero-3-P appears to be rate-limiting for synthesis and secretion of triglyceride by livers from hyperthyroid animals, whereas the glycero-3-P concentrations in euthyroid livers were sufficient to support maximal production of triglyceride limited only by the supply of free fatty acid.
D000818:Animals; D016632:Apolipoprotein A-I; D001053:Apolipoproteins / Q000378:metabolism; D005947:Glucose / Q000378:metabolism*; D005990:Glycerol / Q000494:pharmacology*; D005994:Glycerophosphates / Q000378:metabolism*; D006980:Hyperthyroidism / Q000378:metabolism*; D007657:Ketone Bodies / Q000378:metabolism*; D007700:Kinetics; D008075:Lipoproteins, HDL / Q000378:metabolism; D008079:Lipoproteins, VLDL / Q000378:metabolism; D008099:Liver / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D010477:Perfusion; D051381:Rats; D011919:Rats, Inbred Strains; D013961:Thyroid Gland / Q000502:physiology*; D014280:Triglycerides / Q000378:metabolism*
D016632:Apolipoprotein A-I; D001053:Apolipoproteins; D005994:Glycerophosphates; D007657:Ketone Bodies; D008075:Lipoproteins, HDL; D008079:Lipoproteins, VLDL; D014280:Triglycerides; C029620:alpha-glycerophosphoric acid; D005947:Glucose; D005990:Glycerol