Acetoacetyl-CoA ligase activity in the isolated rat hepatocyte: Effects of 25-hydroxycholesterol and high density lipoprotein |
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Authors: | Gail A Wong James D Bergstrom John Edmond |
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Institution: | (1) Department of Biological Chemistry, 33-257 CHS, UCLA School of Medicine, 90024 Los Angeles, California;(2) Mental Retardation Research Center, UCLA School of Medicine, 90024 Los Angeles, California |
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Abstract: | The activity of acetoacetyl-CoA (AcAc-CoA) ligase (E.C.6.2.1.16) in hepatocytes from rats was shown to be the same as the activity in homogenates of their livers. In hepatocytes treated with 25-hydroxycholesterol, AcAc-CoA ligase, 3-hydroxy-3-methyl-glutaryl-CoA (HMG-CoA) reductase and rates of sterol synthesis were substantially decreased. Hepatocytes treated with high density lipoprotein (HDL) exhibited a 2 to 4 fold induction of HMG-CoA reductase activity; however an accompanying increase in AcAc-CoA ligase activity and the rate of cholesterol synthesis was not observed. We conclude (a) that increases in the activity of HMG-CoA reductase when mediated by HDL in hepatocytes do not result in a corresponding change in the capacity for sterol synthesis and (b) that changes in the activity state of HMG-CoA reductase can be dissociated from that of AcAc-CoA ligase. |
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Keywords: | rat hepatocyte acetoacetyl-CoA ligase HMG-CoA reductase cholesterol synthesis 25-hydroxycholesterol high density lipoprotein |
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