Rabbit bile acids

Baringhaus KH, Matter H, Stengelin S and Kramer W. Substrate specificity of the ileal and the hepatic Na /bile acid cotransporters of the rabbit. II. A reliable... 

In addition to more rapid absorption of lipids in animals fed casein, another mechanism that may be operative is decreased clearance of circulating lipids. Rabbits fed a casein-based semipurified diet excreted significantly less cholesterol but more bile acids in their feces than animals fed a commercial diet (18). The total sterol excretion in feces of the animals fed the casein diet was half that of the rabbits fed the stock diet. Huff and Carroll (19) found that rabbits fed soy protein had a much faster turnover rate of cholesterol and a significantly reduced rapidly exchangeable cholesterol pool compared with rabbits fed casein. Similar studies performed in our laboratory revealed that the mean transit time for cholesterol was 18.4 days in rabbits fed soy protein, 36.8 days in rabbits fed casein, 33.7 days in rabbits fed soy plus lysine, and 36.3 days in rabbits fed casein plus arginine. These data suggest that addition of lysine to soy protein... 

Although absolute proof is still lacking it seems clear that NTCP is the major sodium-dependent transporter of bile acids, although a minor role for other proteins cannot be excluded. It has now been isolated from rat, mouse, rabbit and human. The rat polypeptide was first expressed in Xenopus laevis oocytes and shown to be a 362 amino acid glycoprotein with 7 or 9... 

Chadwick, Y.S., et al. 1979. Effect of molecular structure on bile acid-induced alterations in absorptive function, permeability and morphology in the perfused rabbit colon. J Lab Clin Med Sci 94 661. 

Taurine conjugation with bile acids, phenylacetic acid, and indolylacetic acid seems to be a minor process in most species, but in the pigeon and ferret, it occurs extensively. Other infrequently reported conjugations include serine conjugation of xanthurenic acid in rats excretion of quinaldic acid as quinaldylglycyltaurine and quinaldylglycylglycine in the urine of the cat, but not of the rat or rabbit and conversion of furfural to furylacrylie acid in the dog and rabbit, but not in the rat, hen, or human. The dog and... 

Aldini, R., Montagnani, M., Rods, A., Hivlia, S., Biagi, R, and Rada, E. (1996). Intestinal ab.sorptLon of bile acids in the rabbit Different transport rates in jejunum and ileum. 

Yoshioka, S. Caldwell, L. Higuchi, T. Enhanced rectal bioavailability of polypeptides using sodium 5-methoxysalicylate as an absorption promoter. J. Pharm. Sci. 1982, 71, 593-594. Fasano, A. Budillon, G. Guandalini, S. Cuomo, R. Parrilli, G. Cangiotti, A.M. Morroni, M. Rubino, A. Bile-acids reversible effects on small intestinal permeability —an in vitro study in the rabbit. Dig. Dis. Sci. 1990, 55, 801-808. 

Cholic acid differs from chenodeoxycholic acid in having an extra hydroxyl group at C-12. The enzyme responsible for producing this difference, 7a-hydroxy-4-cholesten-3-one 12a-hydroxylase, thus acts at a key branch point in the biosynthesis of bile acids and might be expected to be regulated in order to control the relative amounts of cholic acid and chenodeoxycholic acid produced. Like other hydroxylation steps in bile acid biosynthesis, 12a-hydroxylation requires a specific form of cytochrome P-450, which is present in the cytochrome P-45OLM4 fraction of rabbit liver microsomes (H6). The activity of I2a-hydroxylase has been postulated to be decreased in patients with liver cirrhosis to explain the low proportion of cholic add relative to chenodeoxycholic add in the bile of these patients (V9). Conversely, the activity of this enzyme may be high in patients with cerebrotendinous xanthomatosis, as the bile of these individuals contains mostly cholic acid... 

Bile acids, Phospholipid Enamine derivatives Sodium salicylate Rabbit, rat, dog... 

Deoxycholic acid can be converted into allodeoxycholic acid in rabbits and rats [159,160], Kallner has shown that this conversion probably occurs by intermediate formation of the corresponding 3-oxo-5/8-, S-oxo-A - and 3-oxo-5a-bile acids [161,162]. Most or all of these reactions are catalysed by intestinal microorganisms. The reactions are reversible and it has been shown that allocholic, allo-chenodeoxycholic, allodeoxycholic and allolithocholic acid can be converted into the corresponding 5j8-bile acids. 

The possibility that the biosynthesis of bile acids is regulated by a negative feedback mechanism was supported by early experiments by Thompson and Vars [206] and Eriksson [207], who showed that the rate of bile acid synthesis in rats increased about 10-fold when a bile fistula is made. Bergstrom and Danielsson demonstrated that duodenal infusion of taurochenodeoxycholic acid in bile fistula rats restored the increased synthesis to a normal rate [208]. Danielsson et al. [44] showed that the cholesterol 7a-hydroxylase activity increased in parallel with the bile acid synthesis after cannulation of the bile duct in rats. In a subsequent work by Mosbach et al., it was reported that the incorporation of isotope from labelled acetate, mevalonate and cholesterol but not from labelled 7a-hydroxycholesterol into bile acids was inhibited by duodenal infusion of taurocholate to bile fistula rats [209]. The incorporation of isotope from labelled acetate, mevalonate and cholesterol but not from labelled 7a-hydroxycholesterol was stimulated in perfused livers of cholestyramine-treated rabbits [210]. It was concluded that there are essentially no rate-limiting steps beyond 7a-hydroxycholesterol in the biosynthesis of bile acids from acetate. Since both cholesterol and bile acid biosynthesis was subjected to negative feedback inhibition by bile acids, it cannot be excluded that inhibition of cholesterol biosynthesis precedes inhibition of the bile acid biosynthesis, and that the latter inhibition is secondary to the former. 

P450 7A1 catalyzes cholesterol 7a-hydroxyla-tion, the rate-limiting step in bile acid S5mthesis. Much has been done in several animal models, including purification of the enz5mie from rabbit and rat liver - . The enz5mie was partially purified from human liver and the cDNA was cloned by several groups in 1990 . ... 

Some recent studies on vitamin transport using membrane vesicles include those of vitamin B6 by rat kidney brush border membranes (Bowman et al, 1990), ascorbic acid by teleost intestinal brush border membranes (Mafha et ai, 1993), biotin by human kidney brush border membranes (Baur and Baumgartner, 1992), pantothenate by human placental brush border membranes (Grassl, 1992), folate and riboflavin by rabbit intestinal brush border membranes (Said and Mohammadkhani, 1993a,b Said et al, 1993), and thiamine by rat small intestine basolateral membranes (Laforenza et al, 1993). Bile acid transport in human placental, rat ileal, and rabbit small intestinal brush border membrane vesicles (Dumaswala et al, 1993 Gong et al, 1991 Kramer et al, 1993) and the effect of vitamin D status... 

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