1
40
2
-
Text
A resource consisting primarily of words for reading. Examples include books, letters, dissertations, poems, newspapers, articles, archives of mailing lists. Note that facsimiles or images of texts are still of the genre Text.
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n/a
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Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).
Pages
659-668
Issue
5
Volume
33
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Dublin Core
The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/.
Title
A name given to the resource
BILE-ACID SYNTHESIS .6. REGULATION OF CHOLESTEROL 7-ALPHA-HYDROXYLASE BY TAUROCHOLATE AND MEVALONATE
Publisher
An entity responsible for making the resource available
Journal of Lipid Research
Date
A point or period of time associated with an event in the lifecycle of the resource
1992
1992-05
Subject
The topic of the resource
3-hydroxy-3-methylglutaryl; 7-alpha-hydroxylase; bile acids; Biochemistry & Molecular Biology; biosynthesis; circadian-rhythm; cloning; coenzyme; enzyme; hepatocytes; hmg-coa reductase; liver; messenger-rna; rat-liver microsomes; reductase; substrate
Creator
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Pandak W M; Vlahcevic Z R; Chiang J Y L; Heuman D M; Hylemon P B
Description
An account of the resource
Taurocholate, a relatively hydrophobic bile salt, is a potent down-regulator of HMG-CoA reductase and cholesterol 7-alpha-hydroxylase (C7-alpha-H), the rate-determining enzymes of the cholesterol and bile acid biosynthetic pathways, respectively. Inhibition of cholesterol synthesis with a bolus dose of mevinolin (lovastatin) a competitive inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, profoundly decreases the specific activity of cholesterol 7-alpha-hydroxylase and rate of bile acid synthesis in rats with complete biliary diversion. It is therefore conceivable that taurocholate may suppress cholesterol 7-alpha-hydroxylase primarily by down-regulating the activity of HMG-CoA reductase. To test this hypothesis, taurocholate was coinfused simultaneously to rats with chronic bile fistula with mevalonate (administered as mevalonolactone), an intermediate in the cholesterol biosynthetic pathway. Mevalonolactone was administered to provide a constant supply of newly synthesized cholesterol to cholesterol 7-alpha-hydroxylase, in order to overcome any inhibitory effect of taurocholate on HMG-Coa reductase. Infusions were started 72 h after biliary diversion, and carried out for an additional 48 h. Complete biliary diversion resulted in an increase in C7-alpha-H specific activity (510%), protein mass (550%), steady-state mRNA levels (1430%), and transcriptional activities (330%) as compared to control rats with intact enterohepatic circulations. When rats with biliary diversion were infused intraduodenally with taurocholate, the specific activities of HMG-CoA reductase and cholesterol 7-alpha-hydroxylase activities decreased by 75% (P < 0.001) and 73% (P < 0.001), respectively. Cholesterol 7-alpha-hydroxylase mass, mRNA, and transcriptional activity decreased after intraduodenal infusion of taurocholate to levels similar to those of rats with an intact enterohepatic circulation. The combination of constant infusion of mevalonate and taurocholate failed to reverse the inhibitory effects of taurocholate on cholesterol 7-alpha-hydroxylase activity, mRNA levels, and in vitro transcriptional rates. These data provide evidence that taurocholate represses cholesterol 7-alpha-hydroxylase at the level of gene transcription, and not via down-regulation of HMG-CoA reductase. Infusion of mevalonate alone to biliary diverted rats did not alter cholesterol 7-alpha-hydroxylase activity or mRNA levels, while leading to a 57% decrease in C7-alpha-H gene transcription. This latter finding suggests that mevalonate or its metabolites may be capable of stabilizing C7-alpha-H mRNA levels while down-regulating transcriptional activity.
Identifier
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n/a
Format
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Journal Article
1992
3-hydroxy-3-methylglutaryl
7-alpha-hydroxylase
BILE acids
Biochemistry & Molecular Biology
biosynthesis
Chiang J Y L
circadian-rhythm
Cloning
coenzyme
enzyme
hepatocytes
Heuman D M
HMG-CoA reductase
Hylemon P B
Journal Article
Journal of lipid research
Liver
messenger-rna
Pandak W M
rat-liver microsomes
reductase
substrate
Vlahcevic Z R
-
Text
A resource consisting primarily of words for reading. Examples include books, letters, dissertations, poems, newspapers, articles, archives of mailing lists. Note that facsimiles or images of texts are still of the genre Text.
URL Address
<a href="http://doi.org/10.1016/0016-5085(95)90083-7" target="_blank" rel="noreferrer noopener">http://doi.org/10.1016/0016-5085(95)90083-7</a>
Rights
Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).
Pages
533-544
Issue
2
Volume
108
Search for Full-text
Locate full-text within NEOMED Library's e-journal collections
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Dublin Core
The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/.
Title
A name given to the resource
FAILURE OF INTRAVENOUS-INFUSION OF TAUROCHOLATE TO DOWN-REGULATE CHOLESTEROL 7-ALPHA-HYDROXYLASE IN RATS WITH BILIARY FISTULAS
Publisher
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Gastroenterology
Date
A point or period of time associated with an event in the lifecycle of the resource
1995
1995-02
Subject
The topic of the resource
3-hydroxy-3-methylglutaryl; bile-acid synthesis; cholesterol; coenzyme; coenzyme-a reductase; feedback-regulation; Gastroenterology & Hepatology; hepatic; hepatocytes; liquid-chromatography; liver; messenger-rna levels; performance; transcriptional regulation
Creator
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Pandak W M; Heuman D M; Hylemon P B; Chiang J Y L; Vlahcevic Z R
Description
An account of the resource
Background/Aims: The decrease in cholesterol 7 alpha-hydroxylase induced by intraduodenal infusion of taurocholate in bile fistula vats may be indirect, i.e., mediated through release or absorption of an intestinal factor in response to the presence of bile salts in the intestine. The aim of this study was to determine if negative feedback regulation of cholesterol 7 alpha-hydroxylase can be shown when equimolar concentrations of taurocholate are administered intravenously, thus bypassing the intestine. Methods: After 96 hours of biliary diversion, taurocholate (36 mu mol.h(-1).100 g rat(-1)) was infused into the rats either intravenously or intraduodenally for the final 24 hours. Livers were then harvested for analysis of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase specific activity, cholesterol 7 alpha-hydroxylase specific activity, messenger RNA levels, and transcriptional activity. Results: Intra-duodenally administered taurocholate significantly decreased HMG-CoA reductase and cholesterol 7 alpha-hydroxyfase specific activity by more than 50% and cholesterol 7 alpha-hydroxylase steady-state messenger RNA levels and transcriptional activity by 50%-75%. In contrast, intravenous administration of taurocholate failed to down-regulate either cholesterol 7 alpha-hydroxylase or HMG-CoA reductase. Conclusions: Passage of taurocholate through the intestine strongly potentiates negative feedback regulation of cholesterol 7 alpha-hydroxylase. A putative intestinal factor, released or absorbed in the presence of bile acids in the intestinal lumen, may play a role in the regulation of bile acid synthesis.
Identifier
An unambiguous reference to the resource within a given context
<a href="http://doi.org/10.1016/0016-5085(95)90083-7" target="_blank" rel="noreferrer noopener">10.1016/0016-5085(95)90083-7</a>
Format
The file format, physical medium, or dimensions of the resource
Journal Article
1995
3-hydroxy-3-methylglutaryl
bile-acid synthesis
Chiang J Y L
Cholesterol
coenzyme
coenzyme-a reductase
feedback-regulation
Gastroenterology
Gastroenterology & Hepatology
hepatic
hepatocytes
Heuman D M
Hylemon P B
Journal Article
liquid-chromatography
Liver
messenger-rna levels
Pandak W M
Performance
transcriptional regulation
Vlahcevic Z R