We have proposed that elevated billiary levels of lithocholic acid, particularly nonsulfated lithocholic acid, may act as an initiator or promoter of gallbladder neoplasia by: 1. predisposing to gallstone formation by stimulating gallbladder mucin secretion, 2. impairing gallbladder mucosal cytoprotection by decreasing the amount of sulfated mucin secreted or 3. directly causing gallbladder epithelial cell proliferation. The purpose of this project is to examine the effect of the sulfated and nonsulfated conjugates of lithocholic acid on hamster gallbladder mucin secretion, mucin composition and cellular proliferation. Mucin secretion and synthesis by gallbladder explants in organ culture from young and old hamsters fed either a single dose or multiple doses or multiple doses of lithocholic acid will be quantitated by determining the incorporation of 3H glucosamine into mucin glycoproteins. Changes in gallbladder mucin composition in response to multiple doses of lithocholic acid will be determined by histochemical staining with Alcian blue (pH 2.5) - PAS for neutral and acidic mucinsd and high iron diamine-Alcian blue (pH2.5) to distinguish sulfomucins from sialomucins. Quantitation of the changes in the proportions of the different types of mucins will be accomplished using morphometeric analytical techniques. As a reflection of gallblader cellular proliferation induced by lithocholic acid, the incorporation of 3H thymidine into DNA will be determined. In order to correlate observed changes in mucin secretion, composition and cellular proliferation with changes in biliary bile acids induced by lithocholic acid feeding, totaly biliary bile acid composition including the proportion of sulfated lithocholic acid conjugates will be determined by a combination of high performance liquid chromatography, enzymatic fluorometry and raioimmunoassay. The results will provide information concerning the effect of lithocholic acid on gallbladder mucosa and its possible role in initiating or promoting gallbladder neoplasia.
