LYSOPHOSPHATIDYLCHOLINE-STIMULATED PROTEIN AND GLYCOPROTEIN PRODUCTION BY HUMAN GALLBLADDER MUCOSAL CELLS

It has been demonstrated in experimental cholecystitis in cats produce d by lysophosphatidylcholine that the development of inflammation is a ssociated with the exsorption of a large amount of protein into the ga llbladder lumen. It was subsequently demonstrated that in feline exper imental cholecystitis the protein produced was albumin and that its pr oduction was decreased by vesicular transport inhibitors, suggesting a n active secretory process. In the present study, the effect of lysoph osphatidylcholine on protein production by fresh, isolated human gallb ladder mucosal cells was evaluated. Isolated gallbladder mucosal cells were incubated with [C-14]leucine for 24 hr in tissue culture medium. The cells readily incorporated the radioactive label into cellular pr otein, a process inhibited by cycloheximide. Exposure of the cells to lysophosphatidylcholine for 1 hr in buffer solution resulted in loss o f intracellular protein into the buffer solution. Exposure of the cell s for 1 hr prior to lysophosphatidylcholine administration to vesicula r transport inhibitors, colchicine, and cytochalasin B and to 4 degree s C culture conditions failed to alter the lysophosphatidylcholine-pro duced passage of the C-14 label extracellularly. SDS-PAGE evaluation o f the protein produced demonstrated that human gallbladder mucosal cel ls continuously produced a 66-kDa protein that was not increased by in creasing concentration of lysophosphatidylcholine and a 14-kDa protein that increased with increasing concentrations of lysophosphatidylchol ine. Employing Western blotting with specific antibodies, the 66-kDa p rotein was demonstrated to not be albumin but a 66-kDa glycoprotein, a nd the 14-kDa protein was demonstrated to contain phospholipase A(2). Human gallbladder mucosal cells produced a protein and glycoprotein in response to lysophosphatidylcholine by a mechanism not related to ves icular transport.