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Histochemically, alkaline phosphatase was localised in epithelial brush-border and capillary endothelium of the lamina propria in 41 gallbladders studied. Three distinct patterns of the brush-border enzyme distribution were observed, namely, complete delineation, patchy localisation and a brush-border totally devoid of enzyme activity. Where no histochemical activity was found, biliary chenodeoxycholate was 50 per cent. higher than in cases of patchy distribution and twice as high as in cases with complete staining of the brush-border. Conversely, biliary cholate levels were significantly higher in completely stained cases. Biliary cholesterol was higher in the cases with no histochemical activity and this was reflected in a significantly higher lithogenic index. Significant quantities of cholesterol esters were found in bile from the focal activity group only. Total alkaline phosphatase activity assayed in gallbladders from 112 patients with cholecystitis and/or lithiasis showed that activity was significantly lower in patients with pigment stones than patients with cholecystitis and/or cholesterol stones. This activity was not related to biliary lipid composition in the 77 bile samples analysed. This evidence indicates that biliary lipid composition is associated with the histochemical distribution of alkaline phosphatase in gallbladder mucosa.

The limiting solubility of cholesterol in bile has been defined by several lithogenic indices which all require determination of phospholipids, cholesterol, and bile salt concentrations. These technically demanding assays are not widely available and restrict general application of lithogenic index studies while the indices in use do not accommodate differences in water content of bile. Consequently, a simple index that requires only measurement of biliary cholesterol concentration and bile dry weight has been assessed by comparison with a commonly used lithogenic index. This simple index correlates well with the conventional sophisticated lithogenic index and is not influenced by use of bile obtained by direct aspiration or by duodenal drainage. Similarly, division into patient groups based on various clinical parameters does not influence the correlation. This simple index will allow routine laboratories to assess bile lithogenicity.

Total and lipid phosphorus were measured in the duodenal aspirate of 24 fasting subjects following an injection of cholecystokinin. The lipid phosphorus values were lower than the total phosphorus, a difference most pronounced in dilute samples. Storage at -20 degrees C over 4 weeks resulted in a loss of over 50% lipid phosphorus. Such alterations in the lipid phosphorus affected the calculation of biliary phospholipid and hence the saturation index of cholesterol in bile causing it to be erroneously elevated. It is concluded that analysis of bile samples should be undertaken on freshly obtained samples and include a preliminary step for the extraction of lipids.

Nineteen patients who received chenodeoxycholic acid 750 mg/day for six months had duodenal bile aspirated before and after treatment. In five patients with hypertriglyceridaemia but no gallstones cholesterol saturation was reversed in every case, the mean cholesterol saturation index (SI +/- standard deviation) changing from 1-38 +/- 0-31 to 0-68 +/- 0-06 (P less than 0-005). In 14 patients with gallstones there was also an improvement in bile cholesterol content, but this was not sufficient to produce mean unsaturation, saturation index changing from 1-55 +/- 0-52 to 1-13 +/- 0-43 (P less than 0-05). Only seven of 14 patients with gallstone achieved cholesterol unsaturation. In four patients with hypertriglyceridaemia and gallstones, mean unsaturation was produced and the saturation index changed from 1-70 +/- 0-45 to 0-86 +/- 0-47 (P less than 0-05). When all nine patients with hypertriglyceridaemia were grouped, the mean saturation index fell from 1-52 +/- 0-40 to 0-76 +/- 0-30 after therapy (P less than 0-001). In contrast the 10 patients without hypertriglyceridaemia showed no significant fall in saturation index which was 1-50 +/- 0-54 before and 1-24 +/- 0-40 after therapy. The ability of chenodeoxycholic acid feeding to improve bile saturation with cholesterol correlated with the presence of hypertriglyceridaemia whether or not gallstones were present. It did not correlate with gallstone dissolution or body weight.

Cholesteryl esters, identified by thin-layer and gas-liquid chromatography followed by mass spectroscopy in a few cases, were found in all human bile samples analysed. The amount varied extensively both in absolute concentration and when expressed as a percentage of the total cholesterol present. In about 30% of samples, the percentage of ester exceeded 4% of total cholesterol but there was no clear association with the presence of cholesterol gallstones or pigment stones, nor was there any association with the lithogenicity of bile.

The effects of four different doses of ursodeoxycholic acid (250, 500, 750, and 1000 mg daily) on biliary lipids were studied in 24 patients with radiolucent gallbladder stones. There was a significant increase in the proportion of ursodeoxycholic acid in bile after all doses, being greatest with 750 and 1000 mg daily. Unsulphated lithocholic acid was also increased in the bile after therapy, while the other major bile acids were reduced. The cholesterol content of bile was reduced by all doses, and this change was most marked after 1000 mg (from 10.9 +/- 1.4 to 5.6 +/- 0.5 mol%, P < 0.01). Biliary cholesterol saturation improved significantly only after 750 and 1000 mg daily.

Giving clofibrate 2 g daily to seven patients significantly increased the biliary cholesterol concentration while the proportion of bile acids fell. Five patients on established clofibrate treatment were given 750 mg of chenodeoxycholic acid (CDCA) daily for one month. Biliary lipid analysis after the CDCA treatment showed a significant fall in the proportion of cholesterol and a rise in that of bile acids. The serum lipid concentrations, which had already been reduced by diet and clofibrate, showed a further significant reduction after the introduction of CDCA. This study suggests that CDCA may be usefully combined with clofibrate to reverse the tendency towards cholesterol saturation of bile and enhance the effect of lowering serum lipid concentrations.

It has hitherto been assumed that the cholesterol in bile simply represents an excretory mechanism for cholesterol surplus to bodily requirements. However, recent evidence suggests that this is not the case and that biliary cholesterol has other functions. The functions consist of a mucosal protective effect against the toxic action of bile-salts and also a role in regulating dietary cholesterol absorption. Biliary cholesterol is clearly more than just an excretory substance and serves other important physiological roles.

Glutathione S-transferase (GST) isoenzymes have been measured by specific radioimmunoassay in human bile samples. GST Mu was found in 50% of samples while GST Pi, GST B1 and GST B2 were present in all samples; GST Pi constituted the major isoenzyme identified. The findings of the radioimmunoassay were confirmed by a one-step purification of GST from bile, using affinity chromatography, followed by their identification using sodium dodecyl sulphate-polyacrylamide gel (SDS-PAGE). Inhibition studies showed that, at the concentrations of bile salts found in bile, GST Pi would have little or no enzymic activity. It is proposed that GST Pi acts as a carrier protein of toxic, non-substrate, ligands to remove as yet unidentified substances from biliary epithelial cells and prevent their reabsorption.