Regulation of cholesterol synthesis in cultured canine intestinal mucosa.
The regulation of intestinal cholesterol synthesis was studied utilizing canine ileal mucosa maintained in organ culture for 6 h. Viability was monitored by light and electron microscopy, measurement of cellular enzymes, and the ability to actively transport a glucose analogue. The activity of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase (EC 1.1.4.3.4), the rate-limiting enzyme of cholesterol synthesis, increased 4-fold during a 6-h culture. A parallel increase occurred in the rate of acetate incorporation into digitonin-precipitable sterols during this period. This increase could be prevented by the addition of cycloheximide to the culture. Pure cholesterol, 7-ketocholesterol, and 25-hydroxycholesterol, when present during the last 4 h of culture, also caused significant suppression of the rise in HMG-CoA reductase activity (final HMG-CoA reductase with the three sterols was 77 +/- 4%, 68 +/- 5%, and 58 +/- 3% of control postculture value). Bile salts at low, nontoxic concentrations also inhibited the increase of enzyme activity (2 mM taurocholate = 63 +/- 3% of control, 0.5 mM taurochenodeoxycholate = 76 +/- 6% of control). In contrast, dog lipoproteins separated by ultracentrifugation failed to significantly affect intestinal cholesterol synthesis in these short term organ cultures.
D000818:Animals; D001647:Bile Acids and Salts / Q000494:pharmacology; D001693:Biological Transport, Active; D002784:Cholesterol / Q000096:biosynthesis* / Q000494:pharmacology; D003513:Cycloheximide / Q000494:pharmacology; D004285:Dogs; D006903:Hydroxymethylglutaryl CoA Reductases / Q000378:metabolism; D007408:Intestinal Absorption; D007413:Intestinal Mucosa / Q000187:drug effects / Q000378:metabolism*; D050356:Lipid Metabolism; D008074:Lipoproteins / Q000494:pharmacology; D009924:Organ Culture Techniques
D001647:Bile Acids and Salts; D008074:Lipoproteins; D002784:Cholesterol; D003513:Cycloheximide; D006903:Hydroxymethylglutaryl CoA Reductases