Volume 118, Issue 3, Pages 599-607 (March 2000) Regulation of sterol 12α-hydroxylase and cholic acid biosynthesis in the rat  Z.Reno Vlahcevic*, Gösta Eggertsen‡, Ingemar Björkhem‡, Phillip B. Hylemon§, Kaye Redford*, William M. Pandak*  Gastroenterology  Volume 118, Issue 3, Pages 599-607 (March 2000) DOI: 10.1016/S0016-5085(00)70267-8 Copyright © 2000 American Gastroenterological Association Terms and Conditions

Fig. 1 Bile acid biosynthetic pathways. The classic and alternative pathways are initiated by microsomal CYP7a1 and mitochondrial CYP27, respectively. CYP8b1 uses intermediates in both pathways. Gastroenterology 2000 118, 599-607DOI: (10.1016/S0016-5085(00)70267-8) Copyright © 2000 American Gastroenterological Association Terms and Conditions

Fig. 2 Effects of cholestyramine and hydrophobic bile acid feeding on the SAs of CYP8b1 and CYP7a1. SAs of CYP8b1 and CYP7a1 after cholestyramine (CT; fed as 5% of diet), CA (1%), CDCA (1%), and DCA (0.25%) feeding for 14 days. Data are expressed as percents of paired control values (means ± SE). Gastroenterology 2000 118, 599-607DOI: (10.1016/S0016-5085(00)70267-8) Copyright © 2000 American Gastroenterological Association Terms and Conditions

Fig. 3 Effects of hydrophobic bile acid feeding on the steady-state mRNA levels of CYP8b1 and CYP7a1. CYP8b1 and CYP7a1 steady-state mRNA levels after cholestyramine (CT; fed as 5% of diet), CA (1%), CDCA (1%), and DCA (0.25%) feeding for 14 days. Data are expressed as percents of paired control values (means ± SE). Gastroenterology 2000 118, 599-607DOI: (10.1016/S0016-5085(00)70267-8) Copyright © 2000 American Gastroenterological Association Terms and Conditions

Fig. 4 Transcriptional activities of CYP7a1 and CYP8b1 after CA feeding. Transcriptional activities of CYP8b1 and CYP7a1 after feeding the sodium salt of CA (1% of chow) for 14 days. Nascent mRNAs of CYP8b1, CYP7a1, and rat cyclophilin were elongated in vitro in the presence of [α-32P]guanosine triphosphate (nuclear “run-on” assay). Completed mRNAs were hybridized to their respective cDNAs and vacuum blotted onto nitrocellulose membranes. The ratio of the intensity of CYP8b1 and CYP7a1 to cyclophilin after autoradiography was calculated for each membrane. Data are expressed as percents of paired untreated control values (means ± SE). Gastroenterology 2000 118, 599-607DOI: (10.1016/S0016-5085(00)70267-8) Copyright © 2000 American Gastroenterological Association Terms and Conditions

Fig. 5 Effects of chronic biliary diversion (CBD) on the SAs and steady-state mRNA levels of CYP8b1 (■) and CYP7a1 (▩). SAs and steady-state mRNA levels of CYP8b1 and CYP7a1 after 120 hours of chronic biliary diversion. Data are expressed as percents of values in sham-operated controls (means ± SE). Gastroenterology 2000 118, 599-607DOI: (10.1016/S0016-5085(00)70267-8) Copyright © 2000 American Gastroenterological Association Terms and Conditions

Fig. 6 Effects of intraduodenal infusion of taurocholate (TCA) on the SAs and steady-state mRNA levels of CYP8b1 (■) and CYP7a1 (▩) in rats with chronic biliary diversion. SAs and steady-state mRNA levels of CYP8b1 and CYP7a1 after TCA infusion. After 72 hours of chronic biliary diversion, the sodium salt of TCA (36 μmol/h · 100 g rat−1) was continuously infused intraduodenally for 48 hours. Data are expressed as percents of values in controls with chronic biliary diversion (means ± SE). Gastroenterology 2000 118, 599-607DOI: (10.1016/S0016-5085(00)70267-8) Copyright © 2000 American Gastroenterological Association Terms and Conditions

Fig. 7 Effects of hydrophilic bile acid (UDC and HC) feeding on the SAs and mRNA levels of CYP8b1 (■) and CYP7a1 (▩). SAs of CYP8b1 and CYP7a1 after ursodeoxycholic acid (UDC) (fed as 1% of diet) and hyocholic acid (HC) (fed as 1% of diet) feeding for 14 days. Data are expressed as percents of paired control values (means ± SE). Gastroenterology 2000 118, 599-607DOI: (10.1016/S0016-5085(00)70267-8) Copyright © 2000 American Gastroenterological Association Terms and Conditions

Fig. 8 Effects of cholesterol plus bile acid feeding on the SAs of CYP8b1 and CYP7a1. SAs of CYP8b1 and CYP7a1 after cholesterol (Chol; fed as 4% of diet) alone or cholesterol plus CA (1%) or CDCA (1%) feeding for 14 days. Data are expressed as percents of paired control values (means ± SE). Gastroenterology 2000 118, 599-607DOI: (10.1016/S0016-5085(00)70267-8) Copyright © 2000 American Gastroenterological Association Terms and Conditions

Fig. 9 Effects of cholesterol plus bile acid feeding on steady-state mRNA levels of CYP8b1 and CYP7a1. Steady-state mRNA levels of CYP8b1 and CYP7a1 after cholesterol (Chol; fed as 4% of diet) plus CA (1%) or CDCA (1%) feeding for 14 days. Data are expressed as percents of paired control values (means ± SE). Gastroenterology 2000 118, 599-607DOI: (10.1016/S0016-5085(00)70267-8) Copyright © 2000 American Gastroenterological Association Terms and Conditions

Fig. 10 Effects of intravenous squalestatin infusion on CYP8b1 and CYP7a1 SAs. SAs of CYP8b1 and CYP7a1 after squalestatin infusion. After 72 hours of chronic biliary diversion, squalestatin (15 μg/h) was continuously infused intravenously for 24–48 hours. Data are expressed as percents of values in controls with chronic biliary diversion (means ± SE). Gastroenterology 2000 118, 599-607DOI: (10.1016/S0016-5085(00)70267-8) Copyright © 2000 American Gastroenterological Association Terms and Conditions

Fig. 11 Effects of intravenous squalestatin infusion on CYP8b1 and CYP7a1 mRNA levels. After 72 hours of chronic biliary diversion, squalestatin (15 μg/h) was continuously infused intravenously for 24–48 hours. Data are expressed as percents of values in controls with chronic biliary diversion (means ± SE). Gastroenterology 2000 118, 599-607DOI: (10.1016/S0016-5085(00)70267-8) Copyright © 2000 American Gastroenterological Association Terms and Conditions

Fig. 12 Effects of T3 injection on CYP8b1 and CYP7a1 SAs. SAs of CYP8b1 and CYP7a1 24 hours after intraperitoneal T3 injection (50 or 100 μg). Data are expressed as percents of values in sham-injected paired controls (means ± SE). Gastroenterology 2000 118, 599-607DOI: (10.1016/S0016-5085(00)70267-8) Copyright © 2000 American Gastroenterological Association Terms and Conditions

Fig. 13 Diurnal variation of CYP8b1 compared with CYP7a1. SAs and mRNA levels of CYP8b1 and CYP7a1 were measured every 6 hours over a 24-hour period. RNA loading was standardized to rat cyclophilin levels (not shown) as described in Methods. Gastroenterology 2000 118, 599-607DOI: (10.1016/S0016-5085(00)70267-8) Copyright © 2000 American Gastroenterological Association Terms and Conditions