Total Bile Salt Research Articles

Lactobacilli and bile salt hydrolase in the murine intestinal tract

Mice that have a complex intestinal microflora but that do not harbor lactobacilli were used to determine the contribution of lactobacilli to the total bile salt hydrolase activity in the murine intestinal tract. Bile salt hydrolase activity in the ileal contents of these mice was reduced 86% in the absence of lactobacilli and by greater than 98% in the absence of lactobacilli and enterococci compared with samples from conventional mice. Bile salt hydrolase activities were lower in ileal and cecal contents from lactobacillus-free mice colonized with enterococci than in samples from lactobacillus-free mice colonized with lactobacilli. Bile salt hydrolase activity in the duodena, jejuna, ilea, and ceca of reconstituted lactobacillus-free mice colonized by lactobacilli was similar to that in samples from the intestinal tracts of conventional mice. We conclude from these studies that lactobacilli are the main contributors to total bile salt hydrolase activity in the murine intestinal tract.

Effect of hyocholic acid on the prevention and dissolution of biliary cholesterol crystals in mice

Gallstone prevention and dissolution were studied in a mouse model of cholesterol cholelithiasis using hyocholic acid (3 alpha, 6 alpha, 7 alpha-trihydroxy-5 beta-cholanic acid). Addition of hyocholic acid, 0.1 or 0.3%, in the lithogenic diet (1% cholesterol + 0.5% cholic acid) prevented the formation of cholesterol monohydrate crystals in 70 and 90% of cases, respectively. On the other hand, chow diet supplemented with 0.1 or 0.3% hyocholic acid dissolved cholesterol crystals in lithiasic mice in, respectively, 80 and 100% of cases within 12 days. In both protocols, biles were largely supersaturated with cholesterol; lecithin-cholesterol lamellar liquid crystals were responsible for the transport of the excess cholesterol content. The percentage of hydrophilic bile salts (hyocholic acid, hyodeoxycholic acid, beta-muricholic acid) in bile, although moderate (15-50% of total bile salts), appears to induce such liquid crystalline dispersion. This study demonstrates that the balance between hydrophilic and hydrophobic bile salts plays a major role in the prevention and dissolution of cholesterol crystals. It is also shown that the desaturation of biliary cholesterol is not a prerequisite for gallstone dissolution.

Bile Salt Binding Properties of Commonly Used Gastrointestinal Drugs: Maalox, Carafate, and Questran

We have validated a method to measure bile salt binding by Maalox (aluminum hydroxide and magnesium hydroxide), Carafate (sucralfate), and Questran (cholestyramine) in vitro. The method used in this study involves a correction for adherent water volume and thus provides a correct measure of bile salt binding. With this approach, we described the binding properties of Maalox, Carafate, and Questran. The bile salt binding capacities of Carafate and Maalox are limited and do not have physiological or pharmacological significance. On the other hand, we found that Questran has substantial bile salt binding capacity. At the recommended dosage, Questran could deplete the total bile salt pool. We also found that Carafate, although not used as an antacid, has buffering capacity (maintaining a pH of solution in the range 4.2–4.8) which might contribute to its effectiveness as an ulcer treatment drug.

Schistosomatium douthitti: Biochemical and morphological effects of an experimental infection in mice

The pathophysiological changes that occur in mice experimentally infected with Schistosomatium douthitti were studied. Male ICR mice, 6–8 weeks in age, were exposed to 100 cercariae of S. douthitti from infected snails ( Lymnaea catascopium) and sacrificed weekly for a total of 13 weeks. Liver homogenates, serum samples, and histological sections of liver tissue were examined. Results showed that body weights of animals with prepatent infections were higher than those of corresponding controls. After patency, which occurred at 5 weeks, body weights were lower and liver weights were higher resulting in significantly increased liver weight/body weight ratios. Hematocrit values declined progressively in patent infections. Total cholesterol in liver was generally higher in the parasitized groups reaching significance during patency. Values rose with age in both control and parasitized groups, but sooner in the latter. Free cholesterol was increased in the liver of animals with patent infections. Total lipid content of the liver was reduced in the infected animals throughout the study. Both liver glycogen and serum glucose levels in the infected animals rose over the control values. The activity of alkaline phosphatase (E.C.3.1.3.1) was elevated in liver tissue of infected mice. Glutamic-pyruvic transaminase (E.C.2.6.1.2) activity was higher in serum but lower in the livers of animals harboring patent infections. Total bile salt concentration in parasitized animals did not differ appreciably from control values; however, gallbladders were enlarged five times in the infected animals. Histologically, liver sections from infected mice showed granulomas in various stages of formation and degeneration. Granulomas contained from 1 to 40 schistosome eggs. After 6 weeks of infection, granulomas were characterized by many neutrophils and monocytes. Few lymphocytes and eosinophils were present. As the granulomas developed, fibroblasts and connective tissue became more prominent. Glycogen deposits were observed surrounding granulomas and were increased in older infections. Adult worms contained abundant amounts of glycogen and cholesterol in their parenchymal tissues.

Determination of parameters effecting proton relaxation of hepatic and gallbladder biles in dogs

The parameters which are important in causing changes in the T1 and T2 proton magnetic relaxation times of dogs bile were investigated. Three factors were found to be important in causing relaxation in bile: (i) total bile salt concentration; (ii) total protein concentration, and (iii) viscosity. The T1 and T2 values of hepatic and gallbladder biles were found to be independent of specific gravity, osmolarity and electrolyte concentrations. In vitro experiments were conducted with taurocholic acid, bovine serum albumin and porcine stomach mucin to examine the effects of intermolecular interactions on proton relaxation. Relative to each of the molecules alone, various combinations of the bile salt and proteins exhibit relaxation rates of 20 to 60% below theoretically expected values. This influence of in vitro molecular interactions on T1 and T2 is also likely to occur in hepatic and gallbladder biles in vivo. Thus, the effects of complex intermolecular interactions associated with the gallbladder microenvironment complicate but likely will not preclude direct assessment of physiologic data with magnetic resonance imaging.

Effects of intestinal microbial bile salt sulfatase activity on bile salt kinetics in gnotobiotic rats

Hepatic sulfation is thought to promote fecal excretion of lithocholate in humans by impairing the enterohepatic recirculation of the compound. Sulfatases produced by the gut flora may, at least in part, counteract this process. To investigate this interaction, female germfree rats, which are known to excrete considerable amounts of sulfated bile salts, were selectively associated with a bile salt desulfating flora. In these rats nearly all cecal, colonie, and fecal bile salt sulfate esters were hydrolyzed, resulting in a decrease of total fecal bile salt excretion of >25% compared with gnotobiotic rats without a bile salt desulfating flora. Desulfation of allochenodeoxycholate, the major sulfated bile salt in germfree rats, led to an enhanced recirculation and 12α-hydroxylation of the compound in the liver, resulting in an increased fecal output of allocholate. Microbial desulfation of intraperitoneally injected [24-14C]taurolithocholate-3-sulfate caused a fivefold decrease of the fecal plus urinary excretion rate of the isotope to approximately that found for unsulfated [24-14C]taurolithocholate. Coassociation of the gnotobiotic rats with a microflora that normalized the small intestinal transit time and cecal size led to a rise of total fecal bile salt excretion of >30% and a twofold accelerated excretion of both sulfated and unsulfated injected [24-14C]taurolithocholate. We conclude that in rats the gut flora rapidly desulfates intestinal bile salt sulfates, enhancing the enterohepatic recirculation and subsequent hydroxylation of the desulfated bile salts. In addition, these data illustrate the importance of having a well-defined microflora to normalize intestinal transit time and cecal size of gnotobiotic animals when performing kinetic studies of enterohepatic circulating compounds.

Steatorrhea in patients with intrahepatic cholestasis of pregnancy

A prospective study was undertaken to evaluate fat malabsorption during intrahepatic cholestasis of pregnancy (ICP), a disease characterized by a mild cholestasis of short duration appearing in otherwise healthy young women. An abnormal fecal fat excretion (mean 15.8 g/24 h, range 6–31 g/24 h) was demonstrated in 10 of 12 patients with the icteric form of ICP and in 2 of 11 patients with pruritus gravidarum. The increased fecal fat excretion was generally asymptomatic, could be detected as early as 3 wk after the clinical onset of ICP, remained stable during the affected pregnancies, and returned to normal from 3 to 9 wk after delivery. Steatorrhea correlated with the severity of ICP, estimated by serum levels of bilirubin, total bile salts, and glutamic pyruvic transaminase. A significant fall in the maternal weight/height index was detected after the onset of ICP, being more intense in patients with steatorrhea than in those without it (to 92.6% ± 3.0% of initial values versus 96.7% ± 2.8%, respectively; p < 0.05). A high risk of premature deliveries and fetal distress was demonstrated in these patients, also correlating with the severity of ICP. No direct relationship could be established between steatorrhea or maternal nutritional impairment and fetal prognosis.

Evidence for H+ secretion by the in vivo canine gallbladder

In humans and most other species, a decline in pH of gallbladder contents occurs during the concentration of bile. Recent in vitro studies in rabbit, guinea pig, and Necturus gallbladders have strongly suggested mucosal H+ secretion during sodium reabsorption, presumably representing a Na+/H+ exchange. The present in vivo studies are the first attempt to determine whether H+ secretion by the gallbladder can be demonstrated in the living animal. Gallbladder bile was obtained from 27 anesthetized dogs after 12–24-h fasts; 12 samples of common duct bile were also obtained in 3 dogs during variable taurocholate infusion. In common duct bile, observed ranges were as follows: pH, 7.3–7.85; CO2 partial pressure (Pco2), 21–32 mmHg; total CO2 concentration ([TCO2]), 16.4–41.4 mM; total bile salt concentration ([TBS]), 16–93 mM; and [Na], 153–192 mM. In gallbladder bile, respective ranges were as follows: pH, 5.72–7.29; Pco2, 36–101 mmHg; [TCO2], 1.21–15.5 mM; [TBS], 150–305 mM; and [Na], 199–266 mM. In all samples [Na] was linearly related to [TBS]. Carbon dioxide partial pressure increased from a mean of 27.3 mmHg in common duct bile to >100 mmHg in gallbladder bile at [TBS] = 180 mM, then declined to ~36 mmHg as [TBS] increased to >300 mM. Peak Pco2 occurred at pH ~6.4–6.6, then declined as pH decreased to ~5.7. Bile to plasma Pco2 ratios increased from a mean of 1.08 in common duct samples to >2.0 in gallbladder samples at pH ~6.3, then declined to ~1.0 in fully concentrated bile. If the high Pco2 values in bile were solely due to tissue CO2 production, a sustained increase in Pco2 throughout Na+ reabsorption might be expected. The results strongly suggest H+ secretion (HCO3− neutralization), as peak Pco2 occurred when [TBS] was only about 180 mM, long before sodium absorption was complete. It is hypothesized that H+ secretion may have important favorable effects on calcium lithogenicity, reducing the likelihood of the formation of CaCO3− containing gallstones.

Production of secretory immunoglobulin a in rat self-filling blind loops

Abstract The immunoglobulin A (IgA) response to small intestinal bacteria was studied in rats with self-filling blind loops (SFBLs), surgically constructed in continuity with the intestine or at the end of a Roux-en-Y loop (RY-SFBL) so as to avoid filling with chyme. Total bile salt in the RY-SFBL lumen was much lower (4.35 ± 0.8 μmol) than in the SFBL lumen (116 ± 15 μmol), but other parameters, such as the number of anaerobic bacteria and disaccharidase activities were similar. Within 1 wk of establishing the blind loops, they had accumulated at least 14 times as much IgA as found in the normal jejunum. Luminal IgA per milligram mucosal protein was almost as high in the RY-SFBL as in the SFBL, indicating that a significant proportion of the IgA must be nonbiliary and probably mucosal in origin. Oral treatment with lincomycin significantly reduced luminal IgA accumulation in the RY-SFBL. Column chromatography and enzyme-linked immunosorbent assay (ELISA), which employed antirat secretory component antibody, established that the majority of the luminal IgA was nonmonomeric and complexed with secretory component. Centrifugation of luminal contents to separate soluble and particulate bound IgA showed that the RY-SFBL contained a higher proportion of precipitable IgA than either the SFBL or lincomycin-treated RY-SFBL. Immunoglobulin A eluted from the precipitates by KSCN was bound to a greater extent by bacterial sonicates than IgA in the supernatant. For either precipitate or supernatant IgA, the greatest binding was observed when the IgA was obtained from the RY-SFBL. These observations indicate that rat intestinal mucosa rapidly responds to bacterial overgrowth by secreting secretory immunoglobulin A (sIgA) with specificity for luminal bacterial antigens. As the sIgA present within the SFBL is to a certain extent derived from bile, the lower proportion of SFBL sIgA bound by bacterial antigens than of RY-SFBL sIgA suggests that biliary sIgA is less specific for local antigens than the sIgA that is secreted by the local mucosa.

Production of secretory immunoglobulin a in rat self-filling blind loops: Local secretory immunoglobulin a immune response to luminal bacterial flora

The immunoglobulin A (IgA) response to small intestinal bacteria was studied in rats with self-filling blind loops (SFBLs), surgically constructed in continuity with the intestine or at the end of a Roux-en-Y loop (RY-SFBL) so as to avoid filling with chyme. Total bile salt in the RY-SFBL lumen was much lower (4.35 ± 0.8 μmol) than in the SFBL lumen (116 ± 15 μmol), but other parameters, such as the number of anaerobic bacteria and disaccharidase activities were similar. Within 1 wk of establishing the blind loops, they had accumulated at least 14 times as much IgA as found in the normal jejunum. Luminal IgA per milligram mucosal protein was almost as high in the RY-SFBL as in the SFBL, indicating that a significant proportion of the IgA must be nonbiliary and probably mucosal in origin. Oral treatment with lincomycin significantly reduced luminal IgA accumulation in the RY-SFBL. Column chromatography and enzyme-linked immunosorbent assay (ELISA), which employed antirat secretory component antibody, established that the majority of the luminal IgA was nonmonomeric and complexed with secretory component. Centrifugation of luminal contents to separate soluble and particulate bound IgA showed that the RY-SFBL contained a higher proportion of precipitable IgA than either the SFBL or lincomycin-treated RY-SFBL. Immunoglobulin A eluted from the precipitates by KSCN was bound to a greater extent by bacterial sonicates than IgA in the supernatant. For either precipitate or supernatant IgA, the greatest binding was observed when the IgA was obtained from the RY-SFBL. These observations indicate that rat intestinal mucosa rapidly responds to bacterial overgrowth by secreting secretory immunoglobulin A (sIgA) with specificity for luminal bacterial antigens. As the sIgA present within the SFBL is to a certain extent derived from bile, the lower proportion of SFBL sIgA bound by bacterial antigens than of RY-SFBL sIgA suggests that biliary sIgA is less specific for local antigens than the sIgA that is secreted by the local mucosa.

Influence of tauroursodeoxycholic and taurodeoxycholic acids on hepatic metabolism and biliary secretion of phosphatidylcholine in the isolated rat liver

Studies were carried out using an isolated rat liver system to define: (1) the contribution of exogenous phosphatidylcholine (PC) to biliary phospholipid secretion; and (2) its hepatic metabolism during perfusion of the livers with conjugated bile salts with different hydrophilic/Hydrophobie properties. A tracer dose of sn-1-palmitoyl-sn-2-[ 14C]linoleoylPC was injected as a bolus into the recirculating liver perfusate, under constant infusion of 0.75 μmol/min of tauroursodeoxycholate or taurodeoxycholate. The effects on bile flow, biliary lipid secretion, 14C disappearance from the perfusate and its appearance in bile, as well as hepatic and biliary biotransformation were determined. With both the bile salts, about 40% of the [ 14C]PC was taken up by the liver from the perfusate over 100 min. During the same period less than 2% of the given radioactivity was secreted into bile. More than 95% of the 14C recovered in bile was located within the identical injected PC molecular species. The biliary secretion of labeled as well as unlabeled PC, however, was significantly higher in livers perfused with taurodeoxycholate than tauroursodeoxycholate, while the reverse was observed with respect to bile flow and total bile salt secretion. The exogenous PC underwent extensive hepatic metabolization which appeared to be influenced by the type of bile salt perfusing the liver. After 2 h perfusion, the liver radioactivity was found, in decreasing order, in PC, triacylglycerol, phosphatidylethanolamine and diacylglycerol. In addition, the specific activity of triacylglycerol was significantly higher in tauroursodeoxycholate than in taurodeoxycholate-perfused livers ( P< 0.025), while the reverse was true for the specific activity of hepatic PC ( P < 0.01). Because taurodeoxycholate and tauroursodeoxycholate showed opposite effects on both biliary lipid secretion and hepatic PC biotransformations, we conclude that the hepatic metabolism of glycerolipids is influenced by the physicochemical properties of bile salts.

A liquid crystalline phase in human intestinal contents during fat digestion.

A viscous, gel-like phase was found in ultracentrifuged human upper intestinal contents collected during rapid fat lipolysis. This "gel" phase was layered in the ultracentrifuge tube between the micellar and oil phase. The gel contained lipids typical of the micellar and not the oil phase. The concentration of these lipids was higher and the ratio of total bile salts to lipids was lower in the gel than in the micellar phase. The gel, unlike the micellar phase, was birefringent between crossed polarizers. These data demonstrate that lipids in this gel phase can form liquid crystals in the gut during fat digestion.

Pathogenesis of calcium-containing gallstones. Canine ductular bile, but not gallbladder bile, is supersaturated with calcium carbonate.

Calcium precipitation in bile is a requisite event in the initiation and growth of all pigment gallstones. Calcium solubility in bile is thus of great importance. This is the first attempt to define the ion-product of CaCO3 in bile in any species. If the ion-product: [Ca++] X [CO = 3] exceeds solubility product (K'sp), the sample is supersaturated and CaCO3 precipitation is thermodynamically possible. We have recently determined K'sp of calcite to be 3.76 X 10(-8) mol/liter at 37 degrees C and total ionic strength = 0.16 M. Gallbladder (GB) bile was obtained from 15 anesthetized dogs after 12-24-h fasts. Duct bile was obtained from three dogs (n = 12) during variable taurocholate infusion. Samples were assayed for pH, partial pressure of carbon dioxide (PCO2), total bile salt concentration ([TBS]), total calcium concentration ([Ca]), and free calcium ion concentration ([Ca++]). With increasing [TBS] in both GB and duct bile, there was a linear decline in pH, a curvilinear decline in [HCO-3] and [CO = 3], and linear increase in [Ca++] and [Ca]. All ductular samples were supersaturated with CaCO3, with saturation indices (SI) as high as 17.5 and a mean of 8.36 +/- 1.43 (SE). In sharp contrast, none of the GB samples were supersaturated, due to the marked decline in [CO = 3] upon concentration and acidification of bile. In GB bile, the SI ranged from 0.006 to 0.126, with a mean of 0.039 +/- 0.011. The gallbladder thus produced a change in the SI from a value as high as 17.5 to a value as low as 0.006 in concentrated GB bile, which is a nearly 3,000-fold change. The average change in the SI was approximately 215-fold. Since all duct samples were supersaturated, and since the dog does not normally form gallstones, the data support our previous hypotheses that: (a) in canine bile, as in canine pancreatic juice, a nucleating factor is necessary for CaCO3 precipitation; (b) bile salts are important buffers for Ca++ in bile; and (c) normal GB mucosal function (concentration and acidification of bile) plays an important role in reducing CaCO3 lithogenicity in GB bile.

Examination of the Sephadex G10 Beads Uptake Method for Determination of Bile Salt Monomer Concentration in Taurocholate–Lecithin Solutions

Experiments have been undertaken to examine the validity of the method of Ammon and Walter for the determination of bile acid monomer concentrations in taurocholate—lecithin (TC—L) solutions. The procedure involves, basically, the uptake of the bile acid monomer by Sephadex G10 beads (exclusion limits 700Da) in the presence of a suitable aqueous phase marker (raffinose). Several of the experimental variables involved in the bead-washing technique have been critically studied, and good precision in data (SD in the range of ±2–5% of the mean value) has been obtained. Monomer concentrations determined in the absence of lecithin over a wide range (10–70mM) of TC were found to be in agreement with those obtained by Ammon. Most important, however, is the finding that TC monomer concentrations at constant NMBS were found to be constant in all solutions containing or not containing lecithin [here, the nonmixed micelle bile salt (NMBS) is the total bile salt concentration, but not including species involving lecithin, and is determined by dialysis equilibrium experiments].

Regulation of bile salt sulfotransferase isoenzymes by gonadal hormones.

We studied the regulation of hepatic bile salt sulfotransferase activity by gonadal hormones and the effect of gonadal hormones on two bile salt sulfotransferase isoenzymes. Bile salt sulfotransferase enzyme activity was three times greater in the female than in the male rats. Oophorectomy significantly decreased bile salt sulfotransferase activity in the female, but orchidectomy had no effect on bile salt sulfotransferase activity in the male. Estrogen treatment of intact as well as orchidectomized males markedly stimulated the enzyme activity, while testosterone treatment of intact or oophorectomized females did not effect bile salt sulfotransferase activity. We concluded that the 3-fold greater activity in female rats is due to the striking stimulatory effect of estrogen on bile salt sulfotransferase activity, and the testosterone has little or no role in the sexually related differences in bile salt sulfotransferase activity in mature rats. These sex-related differences in bile salt sulfotransferase activity were investigated further using DEAE-Sephadex A50 ion-exchange chromatography of rat hepatic cytosol. Two bile salt sulfotransferase isoenzymes were identified both with an approximate molecular weight of 130,000. Bile salt sulfotransferase I eluted with 0.05 M NaCl, had an isoelectric point at pH 6.8, was stimulated by estrogen, and was responsible for 90% of total bile salt sulfotransferase activity in the mature female. Bile salt sulfotransferase II eluted with 0.14 M NaCl, had an isoelectric point at pH 5.3, was unresponsive to estrogen, and accounted for 75 to 80% of bile salt sulfotransferase activity in the mature male.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of chenodeoxycholate feeding upon the biliary output of plasma membrane enzymes in the rat

In model experiments using human erythrocytes, glycochenodeoxycholate caused extensive membrane damage (as judged by release of membrane phospholipid and acetylcholinesterase and by cell lysis) at approximately 10-fold lower concentrations than glycocholate. Chenodeoxycholate feeding had no effect upon the total protein, bile salt or phospholipid concentration of rat bile, although evidence is presented to suggest an expansion of the bile salt pool occurred. Rats fed chenodeoxycholate showed a dose-dependent enrichment of this bile acid in bile; this occurred mainly at the expense of cholate. Chenodeoxycholate feeding resulted in an increased biliary output of the plasma membrane enzymes alkaline phosphatase and 5′-nucleotidase; the hepatic activities of these enzymes were also increased. In contrast, the biliary output and hepatic activities of two other plasma membrane enzymes, alkaline phosphodiesterase I and l-leucine-β-naphthylamidase, were unaffected by chenodeoxycholate feeding. A greater proportion of all four plasma membrane enzymes studied existed in bile of chenodeoxycholatefed rats in a “soluble” form (as judged by their remaining in the supernatant on centrifugation of bile). These results are discussed in relation to the origin of plasma membrane enzymes in bile and to the potential toxicity of chenodeoxycholate and its conjugates to the membranes of the hepatobiliary system.

Role of taurine in feeding the low-birth-weightinfant

Plasma and urinary taurine concentrations, growth, nitrogen balance, duodenal bile salt concentration and pattern, fecal bile acid excretion, and intestinal fat absorption were determined in appropriate for gestational age low-birth-weight infants fed either a whey-predominant cow milk formula or the same formula supplemented with taurine (45 mumol/kg/day). Mean plasma taurine concentration in the two groups did not differ. Mean urinary taurine concentration in the control and supplemented groups over the entire study period were 2.67 +/- 0.69 and 12.41 +/- 5.20 mumol/dl, respectively (P less than 0.05). Urinary taurine concentration in the supplemented infants, however, decreased significantly during the study period. Neither growth nor nitrogen retention differed between the two groups. Mean duodenal concentrations of taurine as well as glycine conjugates of both cholate and chenodeoxycholate were higher in supplemented infants. Total duodenal bile salt concentration correlated positively with taurine status as reflected by urinary taurine excretion (r = 0.71); this correlation plus the lower duodenal cholesterol concentration in supplemented infants suggests that conversion of cholesterol to bile acids was greater in supplemented infants. Mean intestinal fat absorption in control and supplemented infants, however, did not differ.

The effect of dibutyryladenosine 3',5'-monophosphate on the synthesis of bile salts in isolated hepatocytes from rat.

The effect of dibutyryladenosine 3',5'-monophosphate (Bt2cAMP) on the synthesis of conjugated cholic, chenodeoxycholic and beta-muricholic acids has been investigated. Hepatocytes were incubated with 1 mM Bt2cAMP for 3 h at 37 degrees C. In cells from rats with a basal rate of bile salt synthesis (soft-diet-fed rats) production of conjugated cholic acid was increased about two fold, synthesis of conjugated chenodeoxycholic acid was increased 10-20-fold but formation of its metabolite, conjugated beta-muricholic acid, was decreased by 30-50% in the presence of the cyclic nucleotide. The sum of the amounts of the three bile salts produced (total bile salt synthesis) was increased 30-50% by Bt2cAMP. When hepatocytes were prepared from rats in which bile salt synthesis had been stimulated by feeding the bile salt sequestrant, cholestyramine, Bt2cAMP had no effect on conjugated cholic acid synthesis, increased conjugated chenodeoxycholic acid production 3-5-fold and decreased conjugated beta-muricholic acid synthesis by about 50%. Total bile salt synthesis was unchanged. The ratio of the amount of conjugated cholic acid to conjugated chenodeoxycholic acid + conjugated beta-muricholic acid produced, an indication of the activity of 7 alpha-hydroxycholest-4-en-3-one 12 alpha-hydroxylase, was raised by Bt2cAMP in hepatocytes from soft-diet-fed but not in those from cholestyramine-fed rats. The effects of the cyclic nucleotide on the synthesis of the three bile salts in hepatocytes from soft-diet-fed rats were found to be saturable at a concentration of about 2 mM. Responses were half-maximal at concentrations of Bt2cAMP varying between 0.5 and 1.5 mM. These results suggest that in hepatocytes from rats with a basal rate of bile salt synthesis Bt2cAMP has effects at three different stages in the pathway, at the level of cholesterol 7 alpha-hydroxylase, 7 alpha-hydroxycholest-4-en-3-one 12 alpha-hydroxylase and chenodeoxycholine acid 6 beta-hydroxylase. In cells from rats in which bile salt synthesis has been stimulated only the effect at the chenodeoxycholic acid 6 beta-hydroxylase level is apparent. Bt2cGMP and Bt2cCMP had no effect on the synthesis of any of the bile salts measure, showing that the effects are specific for Bt2cAMP. The ratio of the amounts of the three bile salts found inside the cells to those found in the medium was decreased by about 90% when Bt2cAMP was present in the hepatocyte incubations. This effect was mimicked by Bt2cGMP and to a lesser extent by Bt2cCMP.(ABSTRACT TRUNCATED AT 400 WORDS)

Taurocholate is more potent than cholate in suppression of bile salt synthesis in the rat

Synthesis of bile salts is regulated through negative feedback inhibition by bile salts returning to the liver. Individual bile salts have not been distinguished with regard to inhibitory potential. We assessed inhibition of bile salt synthesis by either cholate or its taurine conjugate in bile fistula rats. After allowing synthesis to maximize, baseline synthesis was determined by measuring bile salt output in four consecutive 6-hr periods. Next, sodium cholate (+[(14)C]cholate) or taurocholate (+[(14)C]taurocholate) was infused into the jugular vein for 36 hr and bile was collected in 6-hr aliquots. Hepatic flux of exogenous bile salt was determined by measuring output of radioactivity in bile divided by specific activity of the infusate. Synthesis was determined during the last four 6-hr periods of infusion by subtracting exogenous bile salt secretion from the total bile salt output. Thirteen studies using cholate and 13 using taurocholate were performed. Hepatic flux of infused bile salt varied from 1 to 12 micro mol/100 g per rat per hr. Percent suppression of synthesis varied directly with hepatic flux of exogenous bile salt for both cholate and taurocholate in a linear fashion (r = 0.66, P < 0.01 and r = 0.87, P < 0.0005, respectively). Slope of the taurocholate line was 7.82 (% suppression/ micro mol per 100 g per hr), while slope of the cholate line was 3.66 (P < 0.05), indicating that taurocholate was approximately twice as potent as cholate in suppression of synthesis. At fluxes of 10-12 micro mol/100 g per hr, taurocholate suppressed synthesis 84 +/- 8 (SEM) % while cholate suppressed synthesis only 42 +/- 12% (P < 0.02). The x-intercept of the taurocholate line was 0.65 ( micro mol/100 g per hr), while that of the cholate line was -1.01 (NS) suggesting that the threshold for initial suppression of synthesis did not differ for these two bile salts. We conclude that taurocholate is a more effective inhibitor of hepatic bile salt synthesis than cholate, and that intestinal deconjugation of bile salts may play a role in the regulation of synthesis.-Pries, J. M., A. Gustafson, D. Wiegand, and W. C. Duane. Taurocholate is more potent than cholate in suppression of bile salt synthesis in the rat.

Rapid quantification on Chromarods of cholesterol, total bile salts and phospholipids from the same microliter sample of human gallbladder bile

Rapid quantification on Chromarods of cholesterol, total bile salts and phospholipids from the same microliter sample of human gallbladder bile