Role of bile salts and trypsin in the pathogenesis of experimental alkaline esophagitis

The pathogenesis of alkaline reflux esophagitis was investigated in an experimental model by assessing individually the influence of different bile salt moieties and trypsin on esophageal mucosa. An isolated segment of rabbit esophagus was perfused at pH 7 with a solution containing the test agent under study, and the severity of mucosal damage was assessed by using as indicators of mucosal integrity transmucosal potential difference, net flux of Na+, and mucosal permeability to two neutral molecules of different sizes, 3H-H2O and 14C-erythritol. The data indicate that the secondary dihydroxy bile salt, deoxycholate, in its deconjugated form was highly injurious to esophageal mucosa; it was the only test agent that caused gross mucosal lesions during the experiment. The respective conjugated bile salt moiety, taurodeoxycholate, had a weaker effect. Also the primary dihydroxy bile salt, chenodeoxycholate, in its deconjugated form caused moderate damage to the mucosa, whereas its conjugated form, taurochenodeoxycholate, had no effect. The effect of the other three bile salts tested--cholate, taurocholate, and taurolithocholate--was negligible. Trypsin also adversely affected the mucosa, but its effect was weaker than that of deoxycholate. The results suggest that the deconjugated bile salts deoxycholate and chenodeoxycholate (which are formed following bacterial colonization of the upper gastrointestinal tract in the absence of gastric acid), the conjugated bile salt taurodeoxycholate, and the proteolytic enzyme trypsin may have significant roles in the pathogenesis of alkaline reflux esophagitis.

Purification and characterization of taurodeoxycholate 7 alpha-monooxygenase in rat liver

Taurodeoxycholate 7 alpha-monooxygenase was purified from rat liver microsomes of phenobarbital-treated rats. The purification was carried out by solubilization of microsomes by cholate, fractionation with polyethylene glycol, affinity chromatography, and hydroxylapatite chromatography. The purified preparation gave a single major band on sodium dodecyl sulfate-polyacrylamide gel electrophoresis and contained 13.5 nmol of cytochrome P-450/mg of protein, which corresponded to 6.8-fold purification from microsomes on the basis of specific heme content. The specific activity of the enzyme expressed by the enzyme activity per mg of enzyme protein was increased 72-fold from microsomes. The molecular weight of the enzyme was estimated to be 54,000 from calibrated polyacrylamide gel electrophoresis. The enzyme activity-pH curve gave a broad peak between pH 7.0 and 7.5. The Michaelis constant for taurodeoxycholate of the enzyme was 33 microM. Absorption spectra of the oxidized form of the enzyme showed a Soret band at 518 nm, typical of the low spin state of cytochrome P-450 and alpha and beta band at 571 and 534 nm, respectively. The CO-difference spectrum of the reduced enzyme showed a band at 450 nm characteristic of cytochrome P-450. Taurodeoxycholate 7 alpha-monooxygenase was reconstituted from the purified enzyme, NADPH-cytochrome P-450 reductase, dilauroylglyceryl-3-phosphorylcholine, and NADPH. The purified enzyme was free from steroid 12 alpha-hydroxylase, 25-hydroxylase, and 26-hydroxylase activities. The enzyme activity was seriously inhibited by nonionic detergents, but ot by aminoglutethimide or by metapyrone.

Effects of sphincter of Oddi bypass on bile acid metabolism in fed and fasted intact and cholecystectomized dogs

The effects of cholecystectomy and sphincter of Oddi bypass on bile acid (BA) metabolism in dogs have been studied. Cholecystectomy and sphincter bypass decreased the BA pool half-life and increased the percent of taurodeoxycholic acid in the pool. A 48-hour fast had no effect on total BA pool size of intact and intact sphincter-of-Oddi-bypassed dogs but caused a marked decrease in cholecystectomized dogs. It was concluded that while the sphincter of Oddi is unnecessary to maintain bile acid pool size in fasting dogs, the gallbladder is. Alimentation is necessary to maintain pool size in cholecystectomized dogs.

Altered gallbladder bile composition in gallstone disease. Relation to gallbladder wall permeability

The possible role of conjugated bile salts in the induction and mediation of acute aseptic cholecystitis has been assessed. Using an experimental model, we determined the passive permeability to fluorescently labelled dextran in the gallbladder wall when exposed to different bile salts, alone or together with lecithin. Both taurocholate (20 mM) and, in particular, taurodeoxycholate (20 mM) markedly increased the transmural passage of dextran, but this effect was inhibited by lecithin (50 mM). Bile from patients with cholesterol gallstones contained relatively more deoxycholates (19.4% +/- 8.6%) and less lecithin (35 +/- 20 mmol/l) than did bile from patients with uncomplicated gastric disease (14.1 +/- 6.0% deoxycholates and 53 +/- 26 mmol lecithin/l). Since deoxycholates are more inflammation-promoting than cholates in several systems, and lecithin is considered necessary for protection against the devastating effects of bile salts, these findings should not be overlooked in current hypotheses on the pathogenesis of acute calculous cholecystitis.

Metabolism of bile acids by strains of Acinetobacter anitratum and Acinetobacter lwoffii

The activity of two species of bacteria: Acinetobacter anitratum and Acinetobacter lwoffii, isolated from jejunum of patients with achlorhydria and Reichel-Polya resection towards bile salts was investigated. These species were not previously tested from this view point. All strains tested hydrolyzed bile salts; conjugates of deoxycholic acid were hydrolyzed more readily than those of cholic acid. This feature may be used as a bacteriological taxonomic criterion.