['Phosphatidylcholine (PC) and sphingomyelin (SM) are the major phospholipids on the outer leaflet of the hepatocyte canalicular membrane. Since cholesterol preferentially associates with SM in detergent-resistant microdomains, we hypothesized that canalicular membrane lipid composition could modulate secretion of the sterol into bile.', 'Male Wistar rats were fed for 10 days with a control diet with or without the plant sterol diosgenin (1% w/w) to induce biliary cholesterol hypersecretion. Thereafter, lipid compositions and phospholipid molecular species were determined in fistula bile and highly enriched canalicular membrane fractions.', 'Despite four-fold higher biliary cholesterol output in diosgenin-fed rats, no differences were observed between canalicular membranes of diosgenin and control groups with respect to cholesterol/phospholipid ratios (0.58 vs 0.62), phospholipid classes and acyl chain compositions of SMs (16:0 > 24:1 > 24:0 > 22:0 > 18:0 > 23:0 > 20:0 > 24:2), or PCs (mainly diacyl 16:0-18:2, 16:0-20:4, 18:0-20:4, and 18:0-18:2). In contrast to canalicular PCs, bile contained more hydrophilic species (mainly diacyl 16:0-18:2 and 16:0-20:4), without differences between both groups. In vitro resistance of purified canalicular membrane fractions against detergents such as Triton X-100 and taurocholate was also similar in both groups.'] Is regulation of biliary cholesterol secretion independent of hepatocyte canalicular membrane lipid composition : a study in the diosgenin-fed rat model?