7α-Hydroxylation of cholestanol by rat liver microsomes

Shefer, Sarah; Hauser, Susan; Mosbach, Erwin H.

doi:10.1016/s0022-2275(20)43099-8

Cited by 236 publications

(8 citation statements)

References 22 publications

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“…No significant effect on the level of 7␣-OH-Chol in microsomes was observed. The increased hepatic microsomal cyp7a activity after dietary administration of 7-keto-Chol as reported by Tamasawa et al (1091) is in contrast to reported in vitro inhibitory effects of 7-keto-Chol on cyp7a activity of liver microsomes (965,1152). Doerner et al (258) studied the effects of the addition of several oxysterols on the levels of cyp7a mRNA in primary rat hepatocytes.…”

Section: B Formation Of 7-oxygenated Sterolsmentioning

confidence: 93%

“…Stravitz et al (965) reported that taurine conjugates of cholic acid and deoxycholic acid caused a concentration-dependent lowering of the levels of mRNA for cyp7a in primary cultures of rat hepatocytes. In contrast, the taurine conjugates of ursodeoxycholic acid, hyodeoxycholic acid, and ursocholic acid had no effect under the same study conditions.…”

Section: B Formation Of 7-oxygenated Sterolsmentioning

confidence: 99%

“…Several studies (753,755,965,1137) have indicated repression of cyp7a by taurocholate at the level of gene transcription. Pandak et al (756) reported that feeding of cholic acid (1% in diet), chenodeoxycholic acid (1% in diet), or deoxycholic acid (0.25% in diet) to male rats resulted in marked reduction of the levels of enzyme activity, mRNA, and transcriptional activity for cyp7a in liver.…”

Section: B Formation Of 7-oxygenated Sterolsmentioning

confidence: 99%

See 2 more Smart Citations

Oxysterols: Modulators of Cholesterol Metabolism and Other Processes

Schroepfer

2000

Physiological Reviews

872

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: B Formation Of 7-oxygenated Sterolsmentioning

confidence: 93%

Section: B Formation Of 7-oxygenated Sterolsmentioning

confidence: 99%

Section: B Formation Of 7-oxygenated Sterolsmentioning

confidence: 99%

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Oxysterols: Modulators of Cholesterol Metabolism and Other Processes

Schroepfer

2000

Physiological Reviews

872

687

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“…Recently it has been also reported that prolonged exposure of carbamate pesticides methomyl and carbosulfan resulted in accumulation of cholesterol in mouse liver and kidney [27,28,35]. This is direct evidence for deficiency of ascorbic acid due to oxidative stress as series of studies provided clear evidence that Ascorbic acid deficiency leads to reduced bile acid synthesis or catabolism of cholesterol due to decreased activity of the microsomal enzyme cholesterol 7α-hydroxylase [36]. Ascorbic acid is important for the hydroxylation of the cholesterol nucleus on C7.…”

Section: Histologic Studiesmentioning

confidence: 97%

Methomyl induced alteration in mice hepatic-oxidative status

Bb¹,

Manawadi²

2010

Int J of Biot Appl

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Methomyl (S-methyl-1-N (methyl carbamoyl) oxy] thio acetimidate, is a N -methyl carbamate broad spectrum insecticide. The methomyl containing technical formulation the "Lannate" was evaluated for its effects on the liver antioxidant contents, oxidative stress by-products and oxidative stress enzyme activities and histopathology in Swiss albino mice. Normal virgin male Swiss albino mice of 90 days old weighing about 25-30g were used in the experiment. The mice were administered 1, 2, 3, and 4mg/kg body wt methomyl for 30 days and effective dose 4 mg for 5, 10, and 20 days to know the dose and durational effect on liver. The mice were sacrificed on day 31 st or 24 hours after the terminal exposure. Liver dissected out freed from adherent tissue and weighed to nearest milligram. The liver histology, estimations of antioxidant contents, oxidative stress by-products and oxidative stress enzyme activities were carried out. Liver antioxidant contents showed that levels of GSH (Glutathione) and ascorbic acid were decreased significantly in mice treated with 2, 3 and 4mg/kg/day methomyl and 4 mg/ kg/ day for 10 and 20days of methomyl treatment, except the level of ascorbic acid was not changed significantly in mice treated with 2 mg/kg body wt. Liver antioxidant products showed that levels of TBARS (thiobarbaturic acid) and protein carbonyl were increased significantly in mice treated with 2, 3 and 4mg/kg/day methomyl and 4 mg/ kg/ day for 10 and 20days of methomyl treatment, except the level of TBARS was not changed significantly in mice treated with 2 mg/kg body wt of methomyl. Liver oxidative stress enzyme activities showed that levels of CAT (Catalase), SOD (super oxide dismutase) and GST (Glutathione-s-transferase) were decreased significantly in mice treated with 2, 3 and 4mg/kg/day methomyl and 4 mg/ kg/ day for 10 and 20days of methomyl treatment. The Histology of liver of mice treated with 2, 3 and 4 mg / kg/ day methomyl and 4 mg / kg/ day for 10 and 20days of duration showed that dilation of central vein, sinusoids between hypertrophied hepatocytes and cytoplasmic vacuolization with loss of radial arrangement of cells. The result of the present study suggests that chronic exposure to methomyl insecticide has deleterious effect on liver. The study also revealed that the methomyl might have affected cell metabolism and cell membrane permeability and detoxification system in liver.

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“…Ή Βιτ-C λαμβάνει μέρος είς τόν μεταβολισμόν τής χοληστερόλης κατά τήν Ιην ύδροξυλίωσιν αυτής, λόγω πιθανώς ένεργοποιήσεως τής 7-α-ύδροξυλάσης, καί τόν σχηματισμόν οϋτω τής 7-α-ύδροξυχολη-στερόλης [87][88][89][90][91][92][93] . Ή σχέσις των επιπέδων χοληστερόλης καί Βιτ-C του όρου ώς καί ή θετική έπίδρασις υψηλών δόσεων ΑΟ έπί των φυσιολογικών ή ηύξημένων επιπέδων χοληστερόλης είς τό αίμα, δεν έχει εισέτι επαρκώς τεκμηριωθή [94][95][96][97][98][99][100][101][102][103][104] .…”

Section: βιολογικαί δράσειςunclassified

Η Επιδρασις Του Ασκορβικου Οξεος (Βιταμινης C) Επι Του Πολλαπλασιασμου Των Κυτταρων Του Ηπατος Νεαρων Μυων

Liakakos¹,

Λιακάκος²

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Μολονότι τό άσκορβικόν οξύ άνεκαλύφθη καί άνεγνωρίσθη ώς βιταμί νη (βιταμίνη C) από 50ετίας περίπου, επί πολλά έτη ένομίζετο ότι ή δράσις του περιωρίζετο εις την πρόληψιν ή θεραπείαν τοΰ σκορβούτου. Ή συνεχής έν τούτοις έρευνα των βιολογικών δράσεων τούτου, έξακολουθή νά άποδεικνύη ότι τό άσκορβικόν οξύ υπεισέρχεται εις πλείστας όσας βιολογικάς διεργασίας τοΰ οργανισμού. Ούτω έθεωρήσαμεν σκόπιμον εις τό Γενικόν Μέρος της παρούσης έρεύνης νά άναφερθώμεν έν συντομία έπίτών σημαντικωτέρων βιολογικών ιδιοτήτων τούτου. Κατά τά τελευταία έτη εντυπωσιακή πράγματι είναι ή έρευνα της δράσε ως του επί τοΰ πολλαπλασιασμού τών κυττάρων τόσον φυσιολογικών όσον καί κακοηθών,πρερχόμενα εξ Ιστών ανθρώπων ή πειραματόζωων. ΑΊέρευναι έν τούτοις αύται αφορούν εις πειράματα in vitro, εις κλινικός παρατηρήσεις, ή εις παρατηρήσεις έπί φυτών, μέ αντικρουόμενα έν πολλοίς αποτελέσματα. 'Επειδή δέν άνεύρομεν μελέτην ή οποία νά αναφέρεται εις πειραματικός παρατηρήσεις in vivo, εις τήν χορήγησιν δηλαδή άσκορβικοΰ οξέος εις υγιή πειραματόζωα καί εις τήν έν συνεχεία μελέτην της επιδράσεως τούτου έπί τοΰ ρυθμού πολλαπλασιασμού τών κυττάρων ενός ή περισσοτέρων οργά νων αυτών, προέβημεν εις τήν παροϋσαν έρευναν ή οποία αποσκοπεί εις τήν συμβολήν της διευκρινήσεως τοΰ ρόλου τοΰ άσκορβικοΰ οξέος έπί τοΰ πολ λαπλασιασμού τών κυττάρων in vivo, ε'ιδικώτερον δέ έπί τοΰ πολλαπλασια σμού τών κυττάρων τοΰ ήπατος νεαρών πειραματόζωων. Τό πειραματικόν μέρος της παρούσης έρεύνης έγένετο εις τό Τμήμα Βιολογίας τοΰ Κέντρου Πυρηνικών Ερευνών «Δημόκριτος». Τόν Σεβαστόν Καθηγητήν της Πειραματικής Φαρμακολογίας τοΰ Πανε πιστημίου 'Αθηνών κ. Δ.Δ. Βαρώνον ευχαριστώ θερμώς διά τήν εύνοϊκήν ε'ισήγησιν τής παρούσης διατριβής, ώς καί διά τάς έπικοδομητικάς παρατη ρήσεις του. Τόν Σεβαστόν Έπικ. Καθηγητήν τής 'Ιστολογίας τοΰ Πανεπιστημίου 'Αθηνών κ. Ι. Βλάχον ευχαριστώ θερμώς διά τήν Ίστολογικήν έξέτασιν τών παρασκευασμάτων. Τόν Σεβαστόν "Εκτ. Καθηγητήν τής Παιδιατρικής τοΰ Πανεπιστημίου 'Αθηνών κ.Δ. Λιακάκον ευχαριστώ θερμώς διά τήν άνάθεσιν εις έμέτής πα ρούσης έρεύνης ώς καί διά τό άμέριστον ενδιαφέρον του καί τήν καθοδήγησίν του προς περάτωσιν τής μελέτης ταύτης.

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7α-Hydroxylation of cholestanol by rat liver microsomes

Cited by 236 publications

References 22 publications

Oxysterols: Modulators of Cholesterol Metabolism and Other Processes

Oxysterols: Modulators of Cholesterol Metabolism and Other Processes

Methomyl induced alteration in mice hepatic-oxidative status

Η Επιδρασις Του Ασκορβικου Οξεος (Βιταμινης C) Επι Του Πολλαπλασιασμου Των Κυτταρων Του Ηπατος Νεαρων Μυων

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