Mucus glycoprotein content of human cholesterol gallstones

Cholesterol gallstones were obtained from patients undergoing cholecystectomy and the mucus glycoprotein extracted. The biliary mucus glycoprotein was separated from other contaminants by Sepharose 4B gel filtration and the PAS staining excluded volume used to estimate mucus glycoprotein content of the gallstones. Hexosamine and sialic acid analysis of the glycoprotein indicated it was compositionally similar to the human mucus glycoprotein from bile. The mucus glycoprotein content of the nine stones analysed individually varied between 0.75 and 2.3 mg (a 3-fold variation) (1.27 +/- 0.16 mg, mean +/- SEM), whereas stone weight varied between 0.076 and 5.885 g (a 77-fold variation) (1.27 +/- 0.63 g, mean +/- SEM). When a pool of smaller stones, average weight 47 mg, was extracted, only 1.73 mg of glycoprotein was isolated, an average of 0.01 mg/stone. Analysis of the mucus glycoprotein by gel filtration on Sepharose 2B showed the majority of the glycoprotein was excluded as is the case with the mucus glycoprotein in bile. These results are consistent with biliary mucus glycoprotein being involved in the initial stages of gallstone formation but not in subsequent growth.