Sensitive and rapid colorimetric immunoenzymometric assay of ferritin in biological samples

We describe a rapid and sensitive enzyme-linked immunosorbent assay (ELISA) for quantifying ferritin in human and rat biological fluids. We used chlorophenol red beta-D-galactopyranoside as the colorimetric substrate of beta-galactosidase (EC 3.2.1.23), which is coupled to specific antibodies to either human or rat liver ferritin. The assay is sensitive (detection limit for human assay = 0.58 micrograms/L and for rat assay = 0.37 micrograms/L), accurate (average recovery for human assay = 93% and for rat assay = 92%), and precise (total CVs for human assay = 2.3-12.2% and for rat assay = 5.6-11.3%). The results correlated well with those of an established immunoradiometric technique (r = 0.99691). This assay has a prolonged shelf-life, is inexpensive, and utilizes a stable colorimetric substrate that requires relatively short incubation.

Lovastatin added to ursodeoxycholic acid further reduces biliary cholesterol saturation

The effects of lovastatin and ursodeoxycholic acid on cholesterol saturation of gallbladder bile were examined, alone and in combination. Nine volunteers were studied before any treatment and after each of three treatment periods: lovastatin, 40 mg, twice a day; ursodeoxycholic acid, 10 mg/kg per day; and the combination of both drugs. Treatment periods were randomly ordered, lasted 4-5 wk, and each was preceded by a 3-wk washout period. Mean cholesterol saturation index decreased from a baseline value of 1.40-0.92 on lovastatin (p less than 0.008). Mean cholesterol saturation index on ursodeoxycholic acid was 0.87 and decreased to 0.70 with the addition of lovastatin (p less than 0.030). There was a strong correlation (r = 0.87, p less than 0.003) between saturation index on ursodeoxycholic acid and the further incremental reduction in saturation index with addition of lovastatin. These findings raise the possibility that addition of lovastatin to ursodeoxycholic acid treatment might improve the efficacy of this bile salt for dissolution of cholesterol gallstones, especially in patients with a suboptimal response to ursodeoxycholic acid.

An improved purification procedure for conjugated bile acids using octadecyl-bonded silica cartridges

A rapid procedure for the extraction of conjugated bile acids from human fluids using pre-packed octadecyl-bonded silica cartridges is described. The method was compared with the other procedures reported in the literature and was found to produce a higher degree of sample purification and to achieve satisfactory accuracy and reproducibility. The present procedure is applicable to the high-performance liquid chromatographic assay of bile acid conjugates in human bile, gastric juice, serum and urine.

Evidence for the synthesis and secretion of APF--a bile lipid associated protein--by isolated rat hepatocytes

Bile lipids are thought to be secreted in a lipoprotein complex in which they are associated with cholesterol and a protein called the anionic polypeptidic fraction (APF). APF is present in both bile and serum HDL. The association of APF with both bile and lipoprotein strongly suggests that hepatocytes may be responsible for the synthesis and secretion of this protein. In the present work we attempted to verify this by studying the incorporation of [14C]leucine into APF in isolated rat hepatocytes and by immunolocalization in cell cultures. Results obtained showed that synthesis of APF by cells follows the same kinetic pattern as albumin and that it was the third most abundant protein in the bile secretion. Immunolocalization confirmed that APF is synthesized in the endoplasmic reticulum of hepatocytes. This protein which appears to be rapidly secreted could be of great value for the specific detection of the lipids destined for bile secretion.

Differences in gallstone structure in primary common bile duct lithiasis and gallbladder lithiasis

Some differences between gallbladder lithiasis and primary common bile duct lithiasis are described. Microbiological cultures and biochemical analyses were carried out on the bile of two groups of patients: 27 suffering from gallbladder and 5 from primary common duct lithiasis. The microstructure and composition of gallstones were also examined by polarized light microscopy and X-ray diffraction. Women predominated in gallbladder lithiasis but not in primary common duct lithiasis group (P less than 0.05) and body weight was higher in the former group (P less than 0.02). Primary common duct lithiasis patients had a higher, although not significant, incidence of duodenal diverticulosis (P = 0.15), and a higher incidence of E. coli-positive cultures in bile (P less than 0.001). No significant difference in the biochemical composition of the bile was found between the groups. Brown pigment stones predominated in primary common duct lithiasis, while cholesterol stones did in gallbladder and secondary common duct lithiasis (P less than 0.0001). Stones formed in the gallbladder generally show linear, radial growths of cholesterol crystals, while those from the common duct present a polystratified, concentric deposition of microgranules composed mainly of pigmentary salts. These differences should be taken into account as additional criteria in the differential diagnosis between primary and secondary common duct lithiasis, as the classical criteria for diagnosing of the former greatly underestimate its actual incidence. The distinction between primary and secondary common duct lithiasis is of practical significance, since each entity requires different treatment.

Measurement of 5-fluorouracil and its active metabolites in tissue

The 5-fluorouracil content of serum, bile, pancreatic juice, liver, pancreas and muscle was measured by reversed-phase high-performance liquid chromatography using a mobile phase of 5 mM 1-heptanesulfonic acid in 5 mM acetic acid. Free or unmetabolized 5-fluorouracil was extracted from samples with a mixture of light petroleum-n-propanol (40:60). The active metabolites of 5-fluorouracil were hydrolyzed with hot perchloric acid to free 5-fluorouracil and the combined 5-fluorouracil content was extracted. The active metabolite fraction was calculated from the difference between the combined and the free fractions. A straight line plot of the peak areas against concentration was achieved and the detection limit was 50 ng/ml. Five minutes after stopping an intravenous infusion of 15 mg/kg of 5-fluorouracil in a dog, the serum contained only the free form, but other body fluids and tissues contained both free and metabolite fractions. The method may be useful to determine the amount of total drug in patient samples.

Separation and determination of molecular species of phosphatidylcholine in biological samples by high-performance liquid chromatography

A method for determining the molecular species composition of phosphatidylcholine in biological samples by reversed-phase high-performance liquid chromatography with dual-wavelength ultraviolet detection is described. The optimum compromise between analysis time and chromatographic resolution under isocratic and isothermal conditions (0.8 ml/min and 32 degrees C, respectively) was obtained with the mobile phase methanol-ethanol (6:4, v/v) containing 20 mM choline chloride-water-acetonitrile (90:7:3, v/v/v). The problems of quantification at 205 nm, due to large differences in the detector response with the degree of unsaturation, were resolved by using the appropriate calibration factors chosen with the ratio of absorbances at 205 and 215 nm. The proposed procedure gave results in good agreement with fatty acid composition in samples of rat bile, liver, liver mitochondria and microsomes determined by gas-liquid chromatography.

Urobilinogen-i is a major derivative of bilirubin in bile of homozygous Gunn rats

Gunn rats lack bilirubin UDP-glycosyltransferases, but diazo-negative derivatives of bilirubin have been described in their bile. In order to investigate this alternative disposal of bilirubin, crude bile samples from Gunn and Wistar rats were directly analysed by h.p.l.c. Besides bilirubin (in Gunn rats) or its glycosides (in Wistar rats), two major compounds were detected. A yellow one corresponded to the previously documented vitamin B-2 and was equally prominent in Gunn rats or Wistar-rat bile. The other compound was colourless, but on standing in contact with air it was spontaneously oxidized to a pinkish-yellow pigment. It was far more prominent in Gunn-rat bile. Analysis of bile obtained after intravenous injection of [14C]bilirubin to Gunn rats demonstrated that this compound was highly labelled. Freezing and thawing of the bile resulted in the formation of a series of diazo-negative derivatives, demonstrating that the original compound was quite labile. Spectral (adsorption and fluorescent) and chromatographic (h.p.l.c., t.l.c. and paper chromatography) analysis of the oxidized form of the labelled compound allowed its identification as urobilin-i. The colourless compound secreted in bile was urobilinogen-i. Administration of neomycin and bacitracin to Gunn rats or gut resection suppressed the biliary excretion of urobilinogen and thus confirmed its intestinal origin. Urobilinogen seems thus to represent the major bilirubin derivative present in Gunn-rat bile. Its breakdown products might represent the so-far-unidentified diazo-negative polar bilirubin derivatives. Since only a small amount of bilirubin is present in Gunn-rat bile, the urobilinogen formed in the intestinal lumen seems to be derived from bilirubin reaching the gut via routes other than the biliary one.

Lack of effect of halofantrine on hepatic drug metabolism in the rat in vivo and in vitro

The effect of the antimalarial drug halofantrine (Hf) on hepatic drug metabolism in the rat has been studied in vivo and in vitro using different model drug substrates. Hf in vitro produced no significant effect on the values of Km and Vmax for aminopyrine N-demethylation or 7-ethoxycoumarin O-dealkylation in microsomes incubated with Hf (0.01-0.1 mM) or on the rate of N-demethylation of aminopyrine or O-dealkylation of Ec in microsomes produced from rats dosed chronically with Hf (200 mg/kg) for 4 days. The disposition of antipyrine (Ap) was investigated in the isolated perfused rat liver preparation (IPRL). Following the administration of bolus doses of Hf (0.5, 2.5 and 5.0 mg) no significant changes were observed in the half-life (t1/2), clearance (Cl) or apparent volume of distribution (Vd) for Ap compared with controls. Pentobarbitone induced sleeping time was also assessed in mice. No significant difference was determined in time to recovery of the righting reflex for mice receiving Hf as single oral doses or chronically over 4 days when compared with appropriate controls. The potential for selective isoenzyme effects was studied in vivo. The three principal urinary metabolites of Ap, norantipyrine (Np), 3-OH and 4-OH Ap were measured in rat urine, with no significant change in urinary recovery of Ap or any of the metabolites in the presence of Hf (1.25 mg/kg i.p.) compared with controls. These results suggest that Hf is not, in contrast to many commonly used quinoline antimalarials, a potent or specific inhibitor of drug metabolism in vitro or in vivo.

Effect of ursodeoxycholic acid administration on bile acid composition in hamster bile

The modification in the composition of bile acids in hamster by the administration of high dose of ursodeoxycholic acid (UDCA) was investigated. Male Golden Syrian hamsters were divided into five groups: a control group, two groups that received 0.5 g of UDCA per 100 g of standard diet during 30 and 60 days and another two groups that received 1 g of UDCA per 100 g of standard diet during 30 and 60 days. After ether anaesthesia the gallbladder was removed and bile was immediately aspirated. Bile acids were determined by high performance liquid chromatography (HPLC). Taurolithocholic (TLCA) and glycolithocholic acids (GLCA) increased significantly in all treated groups. The glyco/tauro ratio of 0.69 in controls became more than 1 in treated animals except in the case of lithocholic acid (LCA) conjugates which remained less than 1. UDCA derivatives increased proportionally to the administered dose and the cholic/cheno ratio diminished significantly. A moderate increase of 3- and 7-keto derivatives of chenodeoxycholic acid (CDCA) was observed in all treated groups but the above mentioned increment was especially evident in 3-keto derivatives. A high percentage of UDCA administered in the hamster was likely transformed to CDCA and the glyco conjugates of the bile acids were the predominant species except for the LCA derivatives.

Disposition and metabolic profiling of the penetration enhancer Azone. I. In vitro studies: urinary profiles of hamster, rat, monkey, and man

Chain-labeled 14C-Azone was intravenously administered to hamster, monkey, and rat, to compare its metabolic profile with that obtained previously in humans after dermal application. Azone-derived radioactivity was excreted predominantly in the urine for both hamster and monkey, which is similar to the disposition in humans. Metabolic profiling in urine revealed extensive systemic metabolism to occur in all species studied. The main fraction of the metabolites was most polar in man, followed by rat, monkey, and hamster. Traces of the parent compound were detectable only in hamster urine. Although some of the polar major human metabolites were also present in rat urine, the animals were unsuitable for collecting metabolites of Azone observed in humans. In rats, complete cleavage of the dodecyl side chain was ruled out by administering Azone that had been labeled at two distinct positions of the molecule. Additionally, oral administration of Azone to rats resulted in the same metabolic profile as intravenous administration, indicating that gastrointestinal metabolism does not occur or is similar to systemic metabolism.

Isolation and identification of a pyrrolic glutathione conjugate metabolite of the pyrrolizidine alkaloid monocrotaline

This report describes the isolation and identification of a monocrotaline-derived, glutathione-conjugated pyrrole obtained from the bile of male Sprague-Dawley rats. Bile obtained from rats given an intravenous bolus of 14C-monocrotaline was fractionated using a series of chromatographic separations. Initial purification with cholestyramine resin removed bile acid and pigment contaminants. Subsequent anion exchange and reversed-phase HPLC separations yielded several fractions that contained the 14C label and tested positive for pyrroles using Ehrlich's reagent. These fractions were analyzed using fast-atom-bombardment tandem mass spectrometry (FAB MS/MS). In addition to glutathione-conjugated dehydroretronecine, at least one other pyrrole present had similar ionic properties. The latter was not present in amounts sufficient for positive identification.

Carry-over of sulphadimidine in the faeces and urine of pigs fed medicated feed

In two experiments sulphadimidine-free pigs were placed in pens previously occupied by pigs fed a diet containing 100 ppm sulphadimidine. Faeces, urine and spilled feed had been removed by scraping the surface of the pens before the new pigs were introduced. The concentration of sulphadimidine in the tissues of the medicated pigs fell below 100 ng/g within 72 hours of withdrawal of the medicated diet and in the fluids the concentration fell below 500 ng/ml within 96 hours. The concentrations in the tissues of the pigs housed in the contaminated pens exceeded 100 ng/g for up to 24 hours but then fell to acceptable concentrations; the concentration of sulphadimidine in body fluids occasionally exceeded 500 ng/ml.

Proportion of conjugated bilirubin in bile in relation to hepatic bilirubin UDP-glucuronyltransferase activity

To elucidate the diagnostic relevance of biliary conjugated bilirubin, biliary bilirubin from normal volunteers (NV), patients with Gilbert's syndrome (GS) and Crigler-Najjar syndrome type II (C-N II), and from various rat strains was fractionated. Biliary bilirubin diglucuronide (BDG) was present at lower levels, and bilirubin monoglucuronide (BMG) and unconjugated bilirubin were present at higher levels in GS and C-N II compared with NV, which is consistent with decreased hepatic bilirubin UDP-glucuronyltransferase activity (BGTA). The level of biliary BDG was higher in Wistar-Kyoto rats and lower in heterozygous (Jj) Gunn rats than in SD and Wistar rats. The hepatic BGTA level in heterozygous (Jj) Gunn rats was decreased to 60% of that in Wistar rats, in accordance with decreased biliary BDG. On the other hand, BGTA in Wistar-Kyoto rats whose biliary BDG level was high, was not different from that of Wistar and SD rats. Thus, a correlation between BGTA and biliary bilirubin fractions may not exist on some occasions.

Isolation of a potent cholesterol nucleation-promoting activity from human gallbladder bile: role in the pathogenesis of gallstone disease

Gallbladder bile contains nucleation-promoting activity that binds to concanavalin A. The activity was found in gallbladder bile from cholesterol gallstone patients but also in gallbladder bile from patients without stones and patients with pigment stones. Bile from patients with multiple cholesterol gallstones contained high concanavalin A-binding nucleation-promoting activity. The activity was much lower in bile samples from pigment stone patients, patients without stones and patients with a solitary cholesterol stone. Serum contained very little activity and no concanavalin A-binding nucleation-promoting activity could be demonstrated in gallbladder mucosa. This suggests that concanavalin A-binding nucleation promoter is produced in the liver or bile duct epithelium. The activity was fully resistant to digestion with pronase but was heat labile and could be destroyed by prolonged incubation with a mixed glycosidase preparation indicating that sugar residues are important for this activity. On a Superose 12 gel permeation column, promoting activity eluted in two major peaks at apparent molecular weights of 150 +/- 30 kD (n = 5) and less than 5 kD respectively. The mobility on the column was not influenced by pronase digestion. The factor with the higher molecular weight could be isolated further by polyacrylamide gel electrophoresis under nondenaturing conditions. On sodium dodecyl sulfate-polyacrylamide gel electrophoresis, the apparent molecular weight of the glycoprotein was 130 kD. In conclusion, gallbladder bile contains nucleation-promoting activity that binds to concanavalin A. The activity is increased in bile from patients with multiple cholesterol gallstones and could therefore play an important role in the pathogenesis of gallstone disease.

[Diagnostic possibilities of mathematical analysis in the evaluation of lithogenicity of the bile]

A simple modification of the triangulation system is suggested for determination of lithogenous potential of bile. Basing on correlation analysis the regression equation is derived for quantitation of total bile acids. This makes time-consuming chromatographic evaluation of bile needless. It is believed sufficient to specify only two parameters (bile acids and cholesterol) as their correlation in a coordinate system allows one to define the zone of cholesterol saturation of bile. A table is presented to simplify calculations.

Absorption, distribution, and elimination of a single oral dose of [14C]tri-o-cresyl phosphate in hens

The absorption, distribution, elimination, and metabolism of a single oral dose of 50 mg (4.6 microCi)/kg of uniformly phenyl-labeled [14C]tri-o-cresyl phosphate (TOCP) was investigated in adult chickens. Three treated hens were killed at each time interval: 0.5, 1, 2, and 5 days. TOCP was absorbed from the gastrointestinal tract and subsequently distributed throughout the body. Generally, the highest concentrations of radioactivity were associated with gastrointestinal tract parts, bile, kidneys, liver, and lungs. Most of the radioactivity (47%) was excreted in the combined fecal-urinary excreta during the first 12 h. Very small fractions of the dose were deposited in egg albumen and egg yolk, 0.12% and 0.24%, respectively during the 5-day study. After 5 days, 99% of the dose was eliminated in excreta. TOCP and its metabolites in bile and the combined fecal-urinary excreta were analyzed by high-performance liquid chromatography and liquid scintillation spectrometry. TOCP and nine of its metabolites were identified. In the bile a TOCP active metabolite, saligenin cyclic-o-cresyl phosphate, was the predominant compound found compared to the parent compound in the excreta. These results suggest that in the hen TOCP is excreted slower than the rat and also undergoes metabolic activation. The absorption, elimination, and metabolic profile of TOCP in the hen may contribute to its sensitivity to delayed neurotoxicity.

[125I]-insulin metabolism by the rat liver in vivo: evidence that a neutral thiol-protease mediates rapid intracellular insulin degradation

The subcellular site where insulin is degraded by rat hepatocytes in vivo is controversial. While several potential insulin-degrading enzyme systems, each with its own characteristic cellular location, are known to exist in the liver, questions remain about which of them participates in the degradation of physiologic doses of insulin. These studies examine the proteases that degrade physiologic doses of [125I]-insulin in vivo to determine (1) when and where initial degradation occurs, and (2) which of the potential degradative enzymes is active. Following injection into the mesenteric veins of male rats, intact [125I]-insulin and its labeled degradation products were analysed by reverse-phase high-performance liquid chromatography (RP-HPLC) of biopsy homogenates. [125I]-insulin was rapidly degraded in vivo; the t 1/2 of degradation was approximately 2.7 minutes. To test for extracellular protease activity, an isolated perfused liver system was employed. [125I]-insulin (or [125I]-glucagon) uptake was controlled by changing the temperature of the perfusion medium. Five minutes after [125I]-insulin injection, surface-bound label was recovered in an acidic (pH 3.5) wash. In perfusion at 15 degrees C, both the internalization and degradation of [125I]-insulin were inhibited; 7.2% of unbound hormone was degraded and 5.1% of surface-bound insulin was degraded. Only 11.4% of unbound insulin and 17.4% of surface-bound insulin were degraded at 35 degrees C. In contrast, 95.5% of unbound glucagon and 89.9% of surface-bound glucagon were degraded at 35 degrees C. Thus, although glucagon degradation occurs at the sinusoidal plasmalemma of perfused livers, the same membrane does not mediate the rapid degradation of insulin observed in vivo. Analysis of the RP-HPLC [125I]-insulin elution profiles from liver biopsy homogenates, and comparison of them to profiles produced by purified proteases, suggested that insulin protease is responsible for most hepatic degradation of physiologic doses of insulin. Some cathepsin D-like activity was also observed in vivo, confirming that two pathways exist for insulin metabolism. The time course over which insulin was degraded was more rapid than previous studies in vitro would have predicted. This suggests that more insulin was receptor-bound at the time of its initial degradation, and that the active protease was soluble and was introduced into endocytic peripheral endosomes within seconds after their formation.

Studies on medicinal resources from livestock. II. Anti-allergic effects of pig bile. (2)

Anti-allergic activities of lyophilized pig bile [( PB]) were examined in mice with picryl chloride-induced contact dermatitis (PC-CD), an experimental model of delayed-type hypersensitivity (DTH; type-IV allergy). PC-CD was markedly inhibited by an oral administration of [PB] within 4 h after but not during 8 to 16 h after challenge with picryl chloride. Anti-inflammatory activities of [PB] were also examined in acetic acid-induced mouse increased vascular permeability, hypotonic-hyperthermic lysis of rat erythrocytes and carrageenin-induced rat hind paw edema. [PB] had no effect on these models. The present study suggests that [PB] inhibits PC-CD through its immuno-modulation in the inductive phase of DTH rather than by an anti-inflammatory action.

[The effect of galbanic acid on the course of experimental hepatitis]

Administration of galbanic acid isolated from the roots of Ferula kopetdaghensis Eug. Kor. to rats orally in a dose of 50 mg/kg was found to improve the course of toxic hepatitis induced by fourfold subcutaneous injections of a 50% oil solution of CCl4. Galbanic acid produced much more earlier than in control normalization of the activity of the enzymes alanine- and aspartataminotransferase in blood serum, increased glycogen content and improved the parameters of the redox potential of lactic acid-pyruvic acid system in the liver. Galbanic acid exerted the antioxidant effect. In the animals with a developed hepatitis receiving galbanic acid there was a more rapid restoration of intensity of bile secretion, synthesis of bile acids and bilirubin, cholesterol excretion as compared with control.

Hepatobiliary compensation for the loss of gallbladder function after cholecystectomy. An experimental study in the cat

The side effects of the removal of a functioning gallbladder are surprisingly few, and it has been suggested, but never demonstrated, that the hepatobiliary tract then adjusts to compensate for the loss of gallbladder function. In this study the effects of cholecystectomy on bile acid kinetics, bile flow, and biliary clearance of mannitol were studied in cats 6-8 weeks after cholecystectomy. An enhanced recycling rate of a diminished bile acid pool was found. The bile flow was reduced and the bile acid concentration in hepatic bile was increased, but fasting bile acid secretion rate was not changed. Both when the bile acid secretion rate was reduced by drainage via an acute bile fistula and when it was enhanced by intravenous infusion of glycocholic acid, there was a lower bile acid-independent flow in the cholecystectomy group. This reduced bile flow after cholecystectomy was not explained by the higher proportion of deoxycholic acid present in the bile of the cholecystectomized animals. Biliary clearance of mannitol, which is supposed to reflect the canalicular inflow, was not reduced, indicating that the reduction in bile flow is explained by a reduced fluid secretion or an enhanced fluid reabsorption in the bile ductules and ducts after cholecystectomy. In this manner the bile ducts compensate for the loss of the absorptive function of the gallbladder after cholecystectomy.

Biliary excretion and conjugation of diacid angiotensin-converting enzyme inhibitors

The metabolism and biliary excretion of the diacid angiotensin-converting enzyme inhibitors enalapril, lisinopril, perindopril and ramipril have been studied in an isolated perfused rat liver model. Inhibitors were presented to the livers at a dose of 100 micrograms. The hepatic clearance of lisinopril was very low (0.072 ml/min) and was hardly excreted into the bile. The clearances of enalapril, perindopril and ramipril were higher at 0.63, 0.87 and 9.9 ml/min, respectively, and were excreted into bile. The amounts of ester prodrugs excreted in bile were 4.0, 6.1 and 14%, respectively, whereas the diacid forms were excreted to the extent of 46, 27 and 71% of the administered dose, respectively, over 4 hr. Glucuronide metabolites were only detected in bile in significant concentrations for perindopril and ramipril. Base hydrolysis of the perfusate samples showed that lisinopril was not significantly metabolized to conjugates and that little metabolism of enalapril occurred other than rapid conversion to the diacid form. However, both perindopril and ramipril were extensively metabolized beyond the diacid form. These differences in hepatic handling can in part be explained by their octanol-buffer partition coefficients but may also be related to the introduction of a bicyclic ring in perindopril and ramipril which increases their ability to be metabolized and excreted into bile. These differences in hepatic handling of angiotensin-converting enzyme are likely to influence their clinical usefulness, particularly in renal and hepatic disease.

High protein and total lipid concentration are associated with reduced metastability of bile in an early stage of cholesterol gallstone formation

Previous studies from this laboratory suggested that high gallbladder protein concentrations as well as excessive dehydration of bile might reduce the normal metastability of human gallbladder bile. This study attempted to identify persons in an early stage of stone formation, when there are crystals but no stones, and to determine the composition of bile under these conditions of reduced metastability. Two hundred twenty-seven patients were studied, 96 without gallstones. Twenty-three of 96 control patients had cholesterol crystals in their bile. Total protein concentration, total lipid concentration, and cholesterol saturation index were greater in control patients with crystals in bile. To determine whether or not cholesterol saturation index alone could account for the presence of crystals, control patients with cholesterol saturation index above the median value of 1.04 were studied. In this case there was no difference in cholesterol saturation index between the 19 crystal-positive (1.27) and 29 crystal-negative patients (1.26), but the difference in total protein and lipid concentrations persisted. Total protein and total lipid concentrations were even higher in crystal-positive sediments containing large numbers of crystals. Sludge seen by ultrasonography was more common in patients with crystal-positive sediments. High protein and lipid concentrations are associated with reduced metastability of bile.