|Budget Amount *help
¥2,000,000 (Direct Cost : ¥2,000,000)
Fiscal Year 1993 : ¥300,000 (Direct Cost : ¥300,000)
Fiscal Year 1992 : ¥700,000 (Direct Cost : ¥700,000)
Fiscal Year 1991 : ¥1,000,000 (Direct Cost : ¥1,000,000)
The hypolipidemic drug ethyl chlorophenoxyisobutyrate (clofibrate) is known to induce peroxisome proliferation and to ve carcinogenic after long term administration to rats and mice. We examined the effects of treatment with this drug for periods of up to 18 months on cytosolic ATP-stimulated and ADP-inhibited acetyl-CoA hydrolase in rat liver. In male donryu albino rats on a diet containing 0.5% clofibrate, the enzyme activity increased to about 2- and 3-fold the initial level permilligram liver protein and cytosolic protein, respectively, and 2-fold per milligram DNA in 3 days, and then remained at this level for up to 18 months. The increased activity in rats receiving clofivrate for 3 months returned to control level within a week when clofibrate was sithdrown. The change in enzyme activity paralleled the change in the amount of enzyme protein determined by immunoblotting with anyibody against purified acetyl-CoA hydrolasa from rat liver cytosol. No liver tumors were detected macro
scopically after administration of clofibrate for 18 months. However, our results suggest that cytosolic acetyl-CoA hydrelase could be an extraperoxisomal marker enzyme induced by this type of drug.
An extramitochondrial acetyl-CoA hydrolase [EC 126.96.36.199] in the rat liver, which is atimulated by ATP and inhibited by ADP, is known to ve extremely cold-labile. During subcellular fractionations at low temperatures (2-4*C), most of the enxyme activity was lost ; however, most could be recovered by rewarming at 37*C in the presence of a high concentration of potassium phosphate. This enabled us to measure the activities of cold-treated samples. The majority of the ATP-stimulated and ADP-imhibited acctyl-Coa hydrolase activity in rat livers was detected in the cytosolic fraction and small amounts were detected in the peroxixomal fraction. The activity of peroxisomal ATP-stimulated acetyl-CoA hydrolasa was not noticeably increased after clofibrate-treatment. However, the cytosolic activity greatly increased after clofibrate treatment. The activity in the isolated peroxisomal fraction per g of liver was about 5% of that in the cytosolic fraction of liver from the control and about 2% in that from clofibrate-treated rats. Vesides having similar nucleotide (ATP and ADP) sensitivity and cold lability, the enzyme protein in the peroxisomal fraction migrated to the same position as the cytosolic acetyl-CoA hydroiase based on Western blot analysis with antibody against purified acetyl-CoA gydrolase from rat liver cytosol. These results suggest that the peroxisomal enzyme and cytosolic enzyme may be the same extity. Less