Peritoneal colonization by human pancreatic cancer cells is inhibited by antisense FUT3 sequence.

Several alpha(1,3/1,4) fucosyltransferases expressed in human pancreatic cancer cells can participate in the biosynthesis of cell surface sialyl-Lewis a and sialyl-Lewis x antigens that contribute to hematogenous metastatis. Previously, we observed a significant increase of the alpha(1,4) fucosyltransferase activity in tumoral pancreatic cell lines, suggesting that FUT3 could be involved in the sialyl-Lewis antigen expression. Therefore, we invalidated the expression of FUT3 by expressing FUT3 antisense sequence in the human pancreatic tumor BxPC-3 cell line, which expresses the alpha(1,4) fucosyltransferase activity and harbors the cell surface sialyl-Lewis antigens. The decrease of FUT3 transcript after transfection of antisense cDNA of FUT3 in these cells results in a substantial reduction of sialyl-Lewis antigen expression on cell surface. This decreased antigen expression was associated with an inhibition of adhesive properties to E-selectin and a decrease of metastatic power of FUT3 antisense-transfected BxPC-3 cells as tested in nude mice. Our study provides evidence that the expression level of FUT3 may regulate the expression of sialyl-Lewis a and sialyl-Lewis x surface antigens and consequently could play an important role in metastatic properties of human pancreatic cancer cells.

Restoration of alpha(1,2) fucosyltransferase activity decreases adhesive and metastatic properties of human pancreatic cancer cells.

The expression of alpha(1,2) fucosyltransferases that catalyze the fucose transfer to galactose of the N-acetyl(iso)lactosamine chain is decreased in human metastatic pancreatic cancer cells. alpha(2,3) Sialyltransferases catalyze the transfer of sialic acid to the same substrate to form, with alpha(1,3/1,4) fucosyltransferases, sialyl-Lewis a and sialyl-Lewis x determinants on cell surface that are involved in pancreatic metastatic invasion. The aim of this study was to determine whether this decrease of alpha(1,2) fucosyltransferase expression can favor the alpha(2,3) sialyltransferase activity to form metastatic sialyl-Lewis antigens. Restoration of alpha(1,2) fucosyltransferase activity in the human pancreatic cancer cell line BxPC-3 was obtained by selecting stable transfectants expressing FUT1. Overexpression of FUTI in BxPC-3 cells resulted in a substantial reduction of sialyl-Lewis antigen expression that correlated with an increase of expression of Lewis y and H-type antigens on cell surface. The modified oligosaccharide structures were preferentially restricted to three major glycoproteins, which could in part be related to mucin-type glycoproteins. The reduction of sialyl-Lewis antigen expression was associated with an inhibition of adhesive properties to E-selectin and a decrease of gastrointestinal metastatic power of BxPC-3 cells after xenograft transplantation into nude mice. This study provides evidence that the expression level of alpha(1,2) fucosyltransferase may regulate the expression of sialyl-Lewis a and sialyl-Lewis x antigens and consequently could play an important role in metastatic properties of human pancreatic cancer cells.

Effects of dexamethasone and linoleic acid on hepatic secretion of biliary lipids and anionic polypeptide factor: In vivo and in vitro studies.

Synthetic glucocorticoids, such as dexamethasone, and diets enriched with unsaturated fatty acids have been shown to stimulate hepatic bile salt synthesis. This fact led us to investigate the effects of dexamethasone and linoleic acid supplementation on bile secretion. Cholesterol (Ch) and phospholipid secretions are bile acid dependent. Ch and phospholipid in bile are also highly bound to a small apoprotein, the anionic polypeptide factor (APF). In bile, APF may play a physiological role in stabilizing cholesterol:phospholipid vesicles and might also be important in the regulatory process of bile lipid secretion. In order to study the factors influencing bile secretion, the biliary secretion rates of bile lipids and APF were experimentally modulated in perfused rat liver (PRL) and HepG2 cells. As expected, dexamethasone induced an increase in the biliary secretion rate of bile salts (BS) in the two models (PRL: 34 up to 67 nmol/l/min/g liver; HepG2 cells: 234% vs. 100% in controls). The bile secretion rates for phospholipids (PRL: from 5 down to 1.5 nmol/l/min/g liver; HepG2 cells: 93 vs. 100% in controls) and APF (PRL: from 0.34 down to 0.12 microg/l/min/g liver; cells: 86 vs. 100% in controls) rapidly decreased independently from those of BS. The data from experimental cell models supplemented with linoleic acid indicated a correlation between the BS and APF levels (APF: 71 and 63%; BS: 161 and 197% vs. 100% in controls). The phospholipid level was regulated independently from that of APF and BS and increased (106 and 111% vs. 100% in controls), while Ch remained nevertheless unchanged. Our data showed that dexamethasone induced changes in bile and that linoleic acid clearly impaired the regulation exerted by the dexamethasone on bile lipids.

Fucosyltransferase activities in human pancreatic tissue: comparative study between cancer tissues and established tumoral cell lines.

Human pancreatic cancer is characterized by an alteration in fucose-containing surface blood group antigens such as H antigen, Lewis b, Lewis y, and sialyl-Lewis. These carbohydrate determinants can be synthesized by sequential action of alpha(2,3) sialyltransferases or alpha(1,2) fucosyltransferases (Fuc-T) and alpha(1,3/1,4) fucosyltransferases on (poly)N-acetyllactosamine chains. Therefore, the expression and the function of seven fucosyltransferases were investigated in normal and cancer pancreatic tissues and in four pancreatic carcinoma cell lines. Transcripts of FUT1, FUT2, FUT3, FUT4, FUT5, and FUT7 were detected by RT-PCR in carcinoma cell lines as well as in normal and tumoral tissues. Interestingly, the FUT6 message was only detected in tumoral tissues. Analysis of the acceptor substrate specificity for fucosyltransferases indicated that alpha(1,2) Fuc-T, alpha(1,3) Fuc-T, and alpha(1,4) Fuc-T were expressed in microsome preparations of all tissues as demonstrated by fucose incorporation into phenyl beta-d-galactoside, 2'-fucosyllactose, N-acetyllactosamine, 3'-sialyl-N-acetyllactosamine, and lacto-N-biose. However, these fucosyltransferase activities varied between tissues. A substantial decrease of alpha(1,2) Fuc-T activity was observed in tumoral tissues and cell lines compared to normal tissues. Conversely, the activity of alpha(1,4) Fuc-T, which generates Lewis a and sialyl-Lewis a structures, and that of alpha(1,3) Fuc-T, able to generate a lactodifucotetraose structure, were very important in SOJ-6 and BxPC-3 cell lines. These increases correlated with an enhanced expression of Lewis a, sialyl-Lewis a, and Lewis y on the cell surface. The activity of alpha(1,3) Fuc-T, which participates in the synthesis of the sialyl-Lewis x structure, was not significantly modified in cell lines compared to normal tissues. However, the sialyl-Lewis x antigen was expressed preferentially on the surface of SOJ-6 and BxPC-3 cell lines but was not detected on Panc-1 and MiaPaca-2 cell lines suggesting that several alpha(1,3) Fuc-T might be involved in sialyl-Lewis x synthesis.

The oncofetal J28 epitope involves fucosylated O-linked oligosaccharide structures of the fetoacinar pancreatic protein.

The fetoacinar pancreatic protein (FAP), characterized by the mAb J28, is an oncofetal form of bile salt dependent lipase (BSDL), the expression of which is related to pancreatic differentiation and neoplastic processes. Because the J28 epitope, recognized by mAb J28, is suggested to be dependent upon carbohydrates, we have attempted to gain information about the structure of this epitope. Indeed, treatment of FAP with sodium periodate abolished the reactivity of the protein to mAb J28, which demonstrates the implication of oligosaccharides in the structure of the J28 epitope. FAP offers both O-linked and N-linked carbohydrate structures, of which, as we have determined, one is involved. Peptides obtained after cyanogen bromide cleavage were desialylated then separated by affinity chromatography on an immobilized peanut agglutinin agarose column. The peptide retained on this column carried out the reactivity with the mAb J28. Although some differences in amino acid analysis were observed, the N-terminal sequence of this peptide correlates with that of the C-terminal part of the enzyme. Carbohydrate analysis of the peptide bearing the J28 epitope revealed fucose, galactose, N-acetylgalactosamine, N-acetylglucosamine, and N-acetylneuraminic acid. The competition observed between mAb J28 and Ulex europaeus I lectin for binding to the J28 epitope suggested that fucose residue alpha (1-2) linked to a galactose residue was implicated in the structure of the J28 epitope. Alternatively, the loss of the mAb J28 reactivity upon treatment of FAP either with bovine kidney or bovine epididymis fucosidase was observed indicating that fucose residues linked at the alpha (1-2) and alpha (1-6) positions may be involved in the establishment of the structure of the J28 epitope. These observations suggest that mAb J28 recognized a particular fucosylated O-linked oligosaccharide structure located at the mucin-like extended C-terminal part of FAP.

Investigation of two glycosylated forms of bile-salt-dependent lipase in human pancreatic juice.

Pure human pancreatic bile-salt-dependent lipase, devoid of its oncofetal glycoform [Mas, E., Abouakil, N., Roudani, S., Miralles, F., Guy-Crotte., O., Figarella, C., Escribano, M. J. & Lombardo, D. (1993) Biochem. J. 289, 609-615], was analyzed on immobilized concanavalin A (ConA). Two variants were separated: an unabsorbed ConA-unreactive fraction; and an absorbed ConA-reactive fraction. Carbohydrate compositions of ConA-reactive and ConA-unreactive fractions were not significantly different, and analysis of 3H-labelled oligosaccharides liberated from these fractions on the ConA-Sepharose column indicated that the fractionation of the bile-salt-dependent lipase on this column depends upon oligosaccharide structures. The activity of the ConA-reactive fraction was however much lower, independent of the substrate (4-nitrophenyl hexanoate or cholesteryl esters), than that of the ConA-unreactive fraction. Therefore, catalytic constants for the hydrolysis of 4-nitrophenyl hexanoate were determined; both fractions had quite similar Km, while the kcat for the ConA-unreactive fraction was 3-4-fold higher than that of the ConA-reactive fraction. ConA-reactive and ConA-unreactive fractions were shown to have slightly different molecular masses and different amino acid compositions. Cleavage patterns after cyanogen bromide treatment of the ConA-reactive and ConA-unreactive fractions suggested that the ConA-reactive (high Mr form) and ConA-unreactive (low Mr form) forms could be different isoforms of the bile-salt-dependent lipase secreted by the human pancreas.

Evidence for apical Na+/H+ exchanger in bovine main pancreatic duct.

The finding of a high PCO2 in basally secreted pancreatic juice of man and dog raises the hypothesis of proton secretion from ductal epithelial cells presumably through a Na+/H+ exchanger. To test this possibility, H+ luminal secretion and Na+ movements were measured in vitro on samples of bovine pancreatic ducts mounted in Ussing-type chambers. The rate of luminal acidification measured by the pH stat method, using bicarbonate-free media gassed with 100% O2, reached 2.75 muEq/cm2/hr. Proton secretion was blocked in the presence of 1 nM amiloride or in the absence of Na+ (replaced by choline) in the mucosal solution. Study of transepithelial 22Na fluxes in short-circuited tissue, bathed on both sides by control Ringer solution, gassed by 95% O2-5% CO2 demonstrated a net sodium transport from the mucosal to the interstitial side of the duct (net 22Na flux = 3.23 +/- 0.8 muEq/cm2/hr). This net sodium transport was electroneutral and blocked by mucosal amiloride (0.5-1 mM/liter) or by interstitial ouabain (1 mM/liter). These results are consistent with the existence of a Na+/H+ exchanger on the luminal side of the bovine main pancreatic duct.

Modulating effects of bile salt hydrophobicity on bile secretion of the major protein of the bile lipoprotein complex.

Bile lipids are secreted in association with a newly identified major apoprotein called anionic polypeptide fraction-calcium binding protein (APF-CBP), which is synthesized in the hepatocytes and has been detected in both bile and plasma and characterized. The secretion of the lipids in bile depends both on the concentration and the hydrophobicity of the bile salts (BS) secreted. The present study was undertaken to determine whether the synthesis and the secretion of APF-CBP are similarly regulated by BS, using two methods. The synthesis and secretion of labelled, newly synthesized APF-CBP by isolated rat hepatocytes were monitored by solid-phase immunoassay. For this purpose, hepatocytes were incubated with either glycodeoxycholate (GDC) or taurocholate (TC). The synthesis and secretion of labelled, newly synthesized APF-CBP by perfused rat liver were measured by immunological enzyme-linked assay (ELISA) upon perfusing the liver with either GDC or TC. We found that (i) the synthesis and the secretion of APF-CBP were increased during either TC or GDC perfusion, but the increase was more pronounced with TC; (ii) in GDC perfusion the APF-CBP levels measured were more closely related to the levels of bile salts and not to phospholipid levels, (iii) when the two bile salts were perfused in reverse order, i.e., first GDC and then TC, the secretion of APF-CBP in bile decreased when GDC was perfused, but increased when TC was perfused. Similar results were obtained in experiments with isolated hepatocytes.(ABSTRACT TRUNCATED AT 250 WORDS)

Monensin action on the Golgi complex in perfused rat liver: evidence against bile salt vesicular transport.

Several studies suggest that bile salts are transported from the basolateral to the canalicular membrane of hepatocytes by a vesicular pathway, possibly in part via the Golgi complex. To test this hypothesis, the present study examined, in the perfused rat liver, the influence of the Na+ ionophore monensin on the biliary secretion of taurocholate and biliary lipids. The effects of the drug have been checked by the study of the ultrastructural modifications of the Golgi complex, secretion of horseradish peroxidase, and bile salt uptake. An infusion of monensin (1, 3, or 5 mumol/L) into the liver induced considerable swelling of the Golgi complex within 5 minutes. After a bolus injection of horseradish peroxidase during monensin infusion, the biliary secretion of the protein was delayed (1 mumol/L monensin) and markedly reduced (5 mumol/L monensin). Bile salt uptake was virtually unchanged except with 5 mumol/L monensin. This suggests that monensin has the same effects on the subcellular traffic in the perfused liver as in cultured cells. After a bolus injection of taurocholate (0.25, 5.0, or 8.5 mumol/100 g body wt) during monensin infusion, the pattern of biliary secretion of the bile salt was identical to that of controls. During continuous infusion of taurocholate, a 10-minute monensin infusion (1 or 3 mumol/L) had no effect on the biliary secretion of taurocholate and on the secretion of lecithin and cholesterol induced by taurocholate. High concentrations (5 mumol/L) or prolonged infusions (20 minutes) of monensin decreased the biliary secretion of bile salts but corresponded to a marked decrease of taurocholate uptake. In summary, the Na+ ionophore monensin altered the Golgi complex and the vesicular transport of horseradish peroxidase, whereas taurocholate biliary secretion was not influenced unless taurocholate biliary secretion was not influenced unless taurocholate uptake by the liver was markedly decreased. It may be concluded that taurocholate and biliary lipid secretion, under these conditions, does not depend essentially on pathways involving acidic transporting vesicles and particularly the trans-Golgi complex.

Influence of lipid-rich diets on intestinal cholesterol uptake.

The purpose of this work was to determine whether or not cholesterol transport by intestinal brush border is influenced by fat-enriched diets and therefore plays a role in the regulation of cholesterol absorption. This study was carried out on rats divided into three groups according to diet: (1) control with a diet containing 1.2% cholesterol (diet T), (2) diet T plus 28% saturated fat (lard) and (3) diet T plus 28% polyunsaturated fat (corn oil). Uptake of cholesterol and oleic acid from defined mixed micellar solutions was studied on two experimental models: everted sacs and brush border vesicles of the intestinal membrane. In vivo cholesterol absorption was measured by the dual isotope plasma ratio method of Zilversmit. Fat-enriched diets decreased both in vivo cholesterol absorption and in vitro cholesterol uptake without any specific effect of unsaturated fats. This suggests that the mechanisms involved in the transport of cholesterol across the brush border membrane may be rate-limiting for cholesterol absorption. Oleate and butyrate uptakes, in contrast, were unaffected by the fat content of the diet.

Hepatic metabolism during acute ethanol administration: a phosphorus-31 nuclear magnetic resonance study on the perfused rat liver under normoxic or hypoxic conditions.

The effect of ethanol metabolism on the energetic parameters and intracellular pH of the isolated perfused rat liver from fed rats was studied by phosphorus-31 nuclear magnetic resonance spectroscopy. This technique allowed us to analyze nondestructively and in real time the role of low oxygen tension on the possible injurious effect of ethanol on the liver cells. A quantitative analysis of nuclear magnetic resonance data recorded on a perfused rat liver within a 30 mm diameter probe has been performed at 80.9 MHz. Under normoxic and normothermic conditions, the levels of phosphorylated metabolites detected by nuclear magnetic resonance were 2.8, 0.3 and 2 mumoles per gm liver wet weight for ATP, ADP and inorganic orthophosphate, respectively. The cytosolic pH was 7.25 +/- 0.05. During a period of 4 min of hypoxia induced by reducing the perfusion flow rate to 25% of its initial value (i.e., from 12 ml to 3 ml per min per 100 gm body weight), the level of ATP dropped to 2.2 mumoles per gm liver wet weight. Concomitantly, ADP and inorganic orthophosphate increased to 0.6 and 3.3 mumoles per gm liver wet weight. Cytosolic pH fell to 7.02 +/- 0.05. Perfusion of the liver with a Krebs medium containing 70 mM (0.4%) ethanol induced a sharp decrease in intracellular inorganic orthophosphate to reach 1.3 mumole per gm liver wet weight and after a lag time of 4 to 6 min, a decrease in ATP level (2.15 mumoles per gm liver wet weight). A large increase in phosphomonoesters (mainly sn-glycerol 3-phosphate) up to 6 mumoles per gm liver wet weight was also observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Intestinal cholesterol and oleic acid uptake from solutions supersaturated with lipids.

To test the role of nonmicellar phases in lipid absorption, intestinal uptake of fatty acids and cholesterol has been studied in vitro from supersaturated and micellar solutions. The micellar solubility limit at equilibrium was established for cholesterol and oleate/monoolein (2:1) at pH 6.7 with 10 mM taurocholate. Uptake by rat intestinal everted sacs was measured during incubation of 5 min. Cholesterol uptake increased linearly with the cholesterol content of micellar or supersaturated solutions up to a supersaturation of 150%. Oleate uptake, by contrast, remained essentially the same from either saturated or supersaturated (130-280%) mixtures. The difference between cholesterol and oleate uptake rates is explained by their distinct effects on micellar size, which is unchanged by cholesterol supersaturation but is increased by oleate. Solutions largely supersaturated (280%) with oleate-monoolein are polydisperse and contain viscous isotropic and paracrystalline phases similar to those observed during lipid absorption. These results suggest that, in the presence of such solutions, uptake occurs from both the micellar saturated and nonmicellar supersaturated phases.

Effect of wheat bran, pectin and cellulose on the secretion of bile lipids in rats.

We assayed the lipid content of bile from rats that had been fed either a standard diet (5% fat) or a high fat diet (25% fat, 1.2% cholesterol) in the presence or in the absence of various dietary fibers (namely, wheat bran, pectin and cellulose). The cholesterol concentration in bile from rats fed the high fat diet plus wheat bran or pectin was lower than that of the rats fed the high fat, high cholesterol diet without fiber. Bile phospholipids did not vary significantly from one group to another. In comparison to the standard diet, the high fat, high cholesterol diet led to a greater ratio of primary to secondary bile salts and a higher level of glycoconjugates. The observed differences may be explained by a variation in the metabolism of bile salts brought about by the difference in diet.

Intestinal cholesterol uptake: comparison between mixed micelles containing lecithin or lysolecithin.

The aim of our study was to define the mechanism by which cholesterol uptake is inhibited by lecithin but not by lysolecithin. The work compared the cholesterol uptake by everted rat jejunal sacs from bile salt-lecithin-cholesterol or bile salt-lysolecithin-cholesterol micelles. The micellar size and the cholesterol saturation were measured. The size or molecular weight increases when the lecithin concentration rises, and the cholesterol uptake decreases and leads to zero when the micelles contain more than 30% lecithin. The size of bile salt-lysolecithin-cholesterol micelles is smaller than that of lecithin micelles in comparable molar ratios. Consistent with this result is the fact that, for a given phospholipid concentration, cholesterol uptake is greater in the presence of lysolecithin than in the presence of lecithin. The diffusion rate of the micelles through the unstirred water layer decreases when micellar size increases. However, the comparison of uptakes from lecithin or lysolecithin micelles similar in size and in cholesterol saturation showed that the cholesterol uptake is still lower for lecithin micelles. This shows that with larger micelles some factor other than micellar size and cholesterol content of the micelles is important. We observe that lysolecithin absorption is 15-fold greater than lecithin absorption. We suggest that lysolecithin absorption results in a rapid supersaturation with cholesterol leading to cholesterol absorption.

Mixed micelle properties and intestinal cholesterol uptake.

The solubilizing powers of taurocholate, taurochenodeoxycholate and tauroursodeoxycholate for monoolein and cholesterol, and the size of the bile salt-monoolein-cholesterol micelles have been determined. For the three bile salt species, the micellar size depends on the saturation with monoolein. As a result, for a given bile salt to monoolein ratio, the taurochenodeoxycholate micelles are smaller than those of taurocholate and both are smaller than those of tauroursodeoxycholate. Intestinal cholesterol uptake has been studied in vitro as a function of the micellar size and the saturation degree with cholesterol. For a given bile salt to monoolein ration and 1) for low cholesterol concentrations, taurocholate leads to the greatest rates of uptake ; 2) for high cholesterol content, taurochenodeoxycholate induces the largest uptake. The specific micellar characteristics of the tauroursodeoxycholate micelles clearly demonstrate why this bile salt is of so little help in the intestinal uptake of cholesterol.

Intestinal cholesterol uptake from mixed micelles. In vitro effects of taurocholate, taurochenodeoxycholate and tauroursodeoxycholate.

Cholesterol uptake by everted rat jejunal sacs is lower from mixed micelles containing tauroursodeoxycholate than from those with taurocholate or taurochenodeoxycholate. This occurs in spite of a greater saturation with cholesterol of tauroursodeoxycholate micelles as measured by equilibrium solubility studies. The results suggest that cholesterol saturation of solutions containing tauroursodeoxycholate is overestimated when calculated with reference to solubility in micellar form.

Comparative effects of cholic, chenodeoxycholic, and ursodeoxycholic acids on micellar solubilization and intestinal absorption of cholesterol.

Cholesterol absorption was studied in mice receiving cholic, chenodeoxycholic, or ursodeoxycholic acids (0.2% of the diet) for 2 months. Cholesterol absorption was greater with cholic acid (79%) than with chenodeoxycholic acid feeding (60%) and the lowest levels were observed during ursodeoxycholic acid feeding (37%). Under the three diets, bile acid pool and bile acid secretion were not different. Biliary cholesterol secretion was increased by cholic acid. The bile acid fed represents at least 80% of total bile acids. Micellar solubilization of oleic acid and cholesterol in the presence of each tauro-conjugated bile salt (10 mM) was determined in vitro by the coprecipitation method. Whatever the pH conditions, taurochenodeoxycholate solubilized significantly more cholesterol and more oleic acid than taurocholate. Tauroursodeoxycholate had the poorest detergent properties for both lipids. The differences between the three bile salts for cholesterol solubilization were enlarged by lowering pH and by high oleic acid concentration. Therefore the decrease in cholesterol absorption observed during ursodeoxycholic acid feeding could be explained by the poor detergent properties of this bile salt species. On the other hand, there is no relationship between the detergent properties of taurochenodeoxycholate and taurocholate and their effects on cholesterol absorption in mice. These results suggest that, in this particular case, micellar solubilization is not the rate limiting step in cholesterol absorption.

[Effect of cholic acid and chenodesoxycholic acid on biliary secretion in mice. Effect of the addition of beta-sitosterol]. / Action de l'acide cholique et de l'acide chénodesoxycholique sur la sécrétion biliaire de la souris. Effet de l'addition du beta-sitostérol.

Five groups of 20 mice received for 4 months one of the following diets: T, standard diet (T); a, T + cholic acid (0.2%); b, T + cholic acid (0.2%) + beta-sitosterol (2%); c, T + chenodeoxycholic acid (0.2%); d, T + chenodeoxycholic acid (0.2%) + beta-sitosterol (2%). After this time, the cholesterol intestinal absorption and the biliary secretion of lipids were measured. The biliary secretion of cholesterol, the total hepatic cholesterol (23 mg/g liver dry weight), and the intestinal absorption of cholesterol (90% administered dose) were higher in mice fed with cholic acid than in mice fed with chenodeoxycholic acid (hepatic cholesterol, 9.6 mg/g liver dry weight; absorption, 65% administered dose). The addition of beta-sitosterol to the diet supplemented with cholic acid decreased the cholesterol intestinal absorption and the biliary secretion of cholesterol so that both became similar to that obtained with chenodeoxycholic acid. These results indicate that in mice, as in man, cholic acid elicits a higher cholesterol biliary secretion than chenodeoxycholic acid. In this experimental model, the distinct effect on the biliary cholesterol of these two bile salts is due to their specific effects on the intestinal absorption of cholesterol.