Diurnal variation of HMG-CoA reductase activity in rat liver peroxisomes

1987 ◽  
Vol 148 (2) ◽  
pp. 890-895 ◽  
Author(s):  
Nick Rusnak ◽  
Skaidrite K. Krisans
Keyword(s):  
Diurnal Variation ◽  
Rat Liver ◽  
Reductase Activity ◽  
Hmg Coa Reductase ◽  
Coa Reductase ◽  
Liver Peroxisomes

scholarly journals 3-Hydroxy-3-methylglutaryl coenzyme A reductase localization in rat liver peroxisomes and microsomes of control and cholestyramine-treated animals: quantitative biochemical and immunoelectron microscopical analyses.

1986 ◽  
Vol 103 (3) ◽  
pp. 875-886 ◽  
Author(s):  
G A Keller ◽  
M Pazirandeh ◽  
S Krisans
Keyword(s):  
Rat Liver ◽  
Coenzyme A ◽  
Specific Activity ◽  
Reductase Activity ◽  
Cholesterol Biosynthesis ◽  
Normal Liver ◽  
Hmg Coa Reductase ◽  
The Matrix ◽  
Coa Reductase ◽  
Liver Peroxisomes

3-Hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, a key regulatory enzyme involved in cholesterol biosynthesis, has recently been reported to be present in rat liver peroxisomes (Keller, G.A., M.C. Barton, D.J. Shapiro, and S.J. Singer, 1985, Proc. Natl. Acad. Sci. USA, 82:770-774). Immunoelectron labeling of ultrathin frozen sections of normal liver, using two monoclonal antibodies to purified rat liver microsomal HMG-CoA reductase, indicated that the enzyme is present in the matrix of peroxisomes. This study is a quantitative biochemical and immunoelectron microscopical analysis of HMG-CoA reductase in rat liver peroxisomes and microsomes of normal and cholestyramine-treated animals. Cholestyramine treatment produced a six- to sevenfold increase in the specific activity of peroxisomal HMG-CoA reductase, whereas the microsomal HMG-CoA reductase specific activity increased by about twofold. Using a computer program that calculates optimal linear combinations of marker enzymes, it was determined that between 20 and 30% of the total reductase activity was located in the peroxisomes of cholestyramine-treated animals. Less than 5% of the reductase activity was present in peroxisomes under control conditions. Quantitation of the immunoelectron microscopical data was in excellent agreement with the biochemical results. After cholestyramine treatment there was an eightfold increase in the density of gold particles per peroxisome, and we estimate about a threefold increase in the labeling of the ER.

Reduction of oxysterol levels up-regulates HMG-CoA reductase activity in rat liver

1997 ◽  
Vol 131 (2) ◽  
pp. 237-242 ◽  
Author(s):  
Naoki Tamasawa ◽  
Makoto Hayakari ◽  
Hiroshi Murakami ◽  
Jun Matsui ◽  
Toshihiro Suda
Keyword(s):  
Rat Liver ◽  
Reductase Activity ◽  
Hmg Coa Reductase ◽  
Coa Reductase

2.P.87 Reduction of oxysterol levels up-regulates HMG-CoA reductase activity in rat liver

1997 ◽  
Vol 134 (1-2) ◽  
pp. 134
Author(s):  
Naoki Tamasawa ◽  
Makoto Hayakari ◽  
Hirosi Murakami ◽  
Jun Matsui ◽  
Toshihiro Suda
Keyword(s):  
Rat Liver ◽  
Reductase Activity ◽  
Hmg Coa Reductase ◽  
Coa Reductase

Cholesterol-mediated regulation of HMG-CoA reductase in microsomes from human skin fibroblasts and rat liver

1990 ◽  
Vol 68 (3) ◽  
pp. 674-679 ◽  
Author(s):  
R. George ◽  
P. J. Davis ◽  
L. Luong ◽  
M. J. Poznansky
Keyword(s):  
Tissue Culture ◽  
Enzyme Activity ◽  
Human Skin ◽  
Rat Liver ◽  
Reductase Activity ◽  
Cholesterol Content ◽  
Skin Fibroblasts ◽  
Human Skin Fibroblasts ◽  
Hmg Coa Reductase ◽  
Coa Reductase

3-Hydroxy-3-methylglutaryl-CoA (HMG-CoA) reductase activity was determined in microsomes from human skin fibroblasts and rat liver that had been variously manipulated in vivo or in tissue culture to up- and down-regulate the enzyme. The cholesterol content of these microsomal preparations was then altered by depletion to or enrichment from either cholesterol-free or cholesterol-rich lipid vesicles. Microsomes from human skin fibroblasts responded to cholesterol depletion by increasing HMG-CoA reductase activity and by decreasing it in response to cholesterol enrichment. This was independent of the initial enzyme activity or the tissue culture conditions. Alterations in cholesterol content of rat liver microsomes in vitro failed to demonstrate any significant changes in HMG-CoA reductase activity whether the microsomes started with low enzyme activity (cholesterol-fed rats) or with high enzyme activity (cholestyramine-treated rats). The results are discussed in relation to previously published data and in respect to differences in the control of the human skin fibroblast and rat liver enzymes.Key words: cholesterol, HMG-CoA reductase, microsomes, fibroblasts, rat liver.

scholarly journals A cold-clamping technique for the rapid sampling of rat liver for studies on enzymes in separate cell fractions. Suitability for the study of enzymes regulated by reversible phosphorylation-dephosphorylation

1984 ◽  
Vol 220 (3) ◽  
pp. 733-738 ◽  
Author(s):  
R A Easom ◽  
V A Zammit
Keyword(s):  
Pyruvate Kinase ◽  
Rat Liver ◽  
Reductase Activity ◽  
Respiratory Control ◽  
Hmg Coa Reductase ◽  
Rapid Sampling ◽  
Cell Fractions ◽  
Conventional Manner ◽  
Coa Reductase

A technique for the rapid sampling, cooling and homogenization of rat liver is described. Its effectiveness in preserving the activity status of pyruvate kinase (soluble) and 3-hydroxy-3-methylglutaryl-CoA reductase (HMG-CoA reductase) (microsomal) during sampling is assessed in comparison with that of the freeze-clamping technique and of simple excision and mincing of liver tissue before homogenization. The results suggest that cold-clamping is equally effective as freeze-clamping in preserving the activity status of pyruvate kinase in liver samples obtained in situ, but in addition allows the subsequent separation of subcellular fractions, notably microsomes (microsomal fractions) and mitochondria. It is suggested that this property makes the technique useful in studying the activity status of enzymes (e.g. HMG-CoA reductase) the assay of which is subject to interference from the activity of other enzymes which are released from damaged organelles in crude homogenates of freeze-clamped liver samples. This suggestion was tested directly; the cold-clamping technique was found to preserve a substantially higher initial/total HMG-CoA reductase activity ratio [Easom & Zammit (1984) Biochem. J. 220, 739-745] in subsequently isolated microsomes compared with that obtained in microsomes prepared from liver samples processed in the conventional manner. The integrity of mitochondria isolated from homogenates of cold-clamped liver samples was preserved, as judged by the latency of intramitochondrial enzymes and by good respiratory control of the mitochondria. Possible further areas of metabolic studies to which the cold-clamping technique could be applied are suggested.

scholarly journals Diurnal variation of HMG CoA reductase activity in rat intestine

1972 ◽  
Vol 13 (5) ◽  
pp. 571-573
Author(s):  
S. Shefer ◽  
S. Hauser ◽  
V. Lapar ◽  
E.H. Mosbach
Keyword(s):  
Diurnal Variation ◽  
Reductase Activity ◽  
Rat Intestine ◽  
Hmg Coa Reductase ◽  
Coa Reductase
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