Transformation of labeled cholesterol, 20α-hydroxycholesterol, (22R)-22-hydroxycholesterol, and (22R)-20α,22-dihydroxycholesterol by adrenal acetone-dried preparations from guinea pigs, cattle and man: I. Establishment of radiochemical purity of products

Burstein, Shlomo; Zamoscianyk, Helen; Kimball, Howard L.; Chaudhuri, Ν. Κ.; Gut, Marcel

doi:10.1016/s0039-128x(70)80003-4

Cited by 49 publications

(12 citation statements)

References 17 publications

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“…Rennert et al (844) reported no differences in the retention times of the 22R-and 22Sisomers of 22-OH-Chol upon capillary GC of the free sterols on a DB-17 column. The 22R-and 22S-isomers can be nicely separated by partition chromatography on columns of Celite 545 (149). The 23R-and 23S-isomers of 23-OH-Chol have been reported to have been cleanly separated by simple TLC of their dibenzoate derivatives (1159) and, as the free sterols, by silica gel column chromatography or by TLC (1158,1159) but not by GC as the free sterols or as their diacetate derivatives on SE-30 or QF-1 columns (1158).…”

Section: Chromatographic Separations Of Oxysterol Isomersmentioning

confidence: 99%

Oxysterols: Modulators of Cholesterol Metabolism and Other Processes

Schroepfer

2000

Physiological Reviews

877

687

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Oxygenated derivatives of cholesterol (oxysterols) present a remarkably diverse profile of biological activities, including effects on sphingolipid metabolism, platelet aggregation, apoptosis, and protein prenylation. The most notable oxysterol activities center around the regulation of cholesterol homeostasis, which appears to be controlled in part by a complex series of interactions of oxysterol ligands with various receptors, such as the oxysterol binding protein, the cellular nucleic acid binding protein, the sterol regulatory element binding protein, the LXR nuclear orphan receptors, and the low-density lipoprotein receptor. Identification of the endogenous oxysterol ligands and elucidation of their enzymatic origins are topics of active investigation. Except for 24, 25-epoxysterols, most oxysterols arise from cholesterol by autoxidation or by specific microsomal or mitochondrial oxidations, usually involving cytochrome P-450 species. Oxysterols are variously metabolized to esters, bile acids, steroid hormones, cholesterol, or other sterols through pathways that may differ according to the type of cell and mode of experimentation (in vitro, in vivo, cell culture). Reliable measurements of oxysterol levels and activities are hampered by low physiological concentrations (approximately 0.01-0.1 microM plasma) relative to cholesterol (approximately 5,000 microM) and by the susceptibility of cholesterol to autoxidation, which produces artifactual oxysterols that may also have potent activities. Reports describing the occurrence and levels of oxysterols in plasma, low-density lipoproteins, various tissues, and food products include many unrealistic data resulting from inattention to autoxidation and to limitations of the analytical methodology. Because of the widespread lack of appreciation for the technical difficulties involved in oxysterol research, a rigorous evaluation of the chromatographic and spectroscopic methods used in the isolation, characterization, and quantitation of oxysterols has been included. This review comprises a detailed and critical assessment of current knowledge regarding the formation, occurrence, metabolism, regulatory properties, and other activities of oxysterols in mammalian systems.

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Section: Chromatographic Separations Of Oxysterol Isomersmentioning

confidence: 99%

Oxysterols: Modulators of Cholesterol Metabolism and Other Processes

Schroepfer

2000

Physiological Reviews

877

687

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“…Some doubt has been cast upon this as the only pathway for side-chain cleavage (13)(14)(15)(16)(17). In any case the mechanism of the cleavage step (III) remains uncertain, although this step appears to require TPNH and oxygen (18).…”

Section: A 22-di-oh-cholesterol -Pregnenolonementioning

confidence: 99%

The Stoichiometry of the Conversion of Cholesterol and Hydroxycholesterols to Pregnenolone (3β-Hydroxypregn-5-en-20-one) Catalysed by Adrenal Cytochrome P -450

Shikita¹,

Hall²

1974

Proc. Natl. Acad. Sci. U.S.A.

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“…By the addition of substrate cholesterol to the cytochrome P450scc and the con-trolled supply of electrons and 0., to the reaction mixture, the sequential steps in the conversion of cholesterol to pregnenolone have been elucidated [30]. These studies have confirmed that the hydroxylation reactions follow the pattern cholesterol -22-hydroxycholesterol -20, 22-dihydroxycholesterol -pregnenolone [33], as shown in figure 2.…”

Section: Cam P and Steroidogenesismentioning

confidence: 58%

Dietary Effects on Certain Adrenal Cortical Functions in the Rat

Boyd¹,

Gorban²,

Lawson³

1980

Ann Nutr Metab

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The rate-limiting step in adrenal steroidogenesis is associated with the mitochondrial-cytochrome-P_450scc-dependent production of pregnenolone from cholesterol. This sterol side-chain cleavage reaction is influenced by the supply of cholesterol to the mitochondria. Cholesterol is stored as cholesterol esters while the cytosol contains a hormone-sensitive cholesterol ester hydrolase. This enzyme is activated by phosphorylation involving a cyclic AMP-dependent protein kinase and ATP; this enzyme preferentially attacks cholesterol oleate or cholesterol linoleate. The lipid composition of the adrenal cortex is influenced by diet so that animals on a low-fat diet tend to store cholesterol oleate and as the linoleate content of the diet is increased, the cholesterol linoleate content of the adrenal cortex increases. Animals maintained on a high erucate diet tend to store large amounts of cholesterol erucate in the adrenal cortex; such animals have an impaired adrenal cortical function. Animals maintained on a low-fat diet (marginally deficient in essential fatty acids), a linoleate-replete diet or a moderate erucate diet, all exhibited normal responses to ACTH and normal corticosterone production rates.

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Transformation of labeled cholesterol, 20α-hydroxycholesterol, (22R)-22-hydroxycholesterol, and (22R)-20α,22-dihydroxycholesterol by adrenal acetone-dried preparations from guinea pigs, cattle and man: I. Establishment of radiochemical purity of products

Cited by 49 publications

References 17 publications

Oxysterols: Modulators of Cholesterol Metabolism and Other Processes

Oxysterols: Modulators of Cholesterol Metabolism and Other Processes

The Stoichiometry of the Conversion of Cholesterol and Hydroxycholesterols to Pregnenolone (3β-Hydroxypregn-5-en-20-one) Catalysed by Adrenal Cytochrome P -450

Dietary Effects on Certain Adrenal Cortical Functions in the Rat

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