BILE-SALT HYDROPHOBICITY MODULATES SUBSELECTION OF BILIARY LECITHIN SPECIES IN RATS DEPLETED OF BILE-SALT POOL

Although bile salts play an important role in the secretion of biliary lipid, little is known about the relationship between bile salt hydro phobicity and the selection of lecithin species to be secreted into bi le. We therefore investigated whether bile salts modulate the selectio n of biliary lecithin subspecies. Rats that were depleted of the bile salt pool were infused with taurocholate (50, 100, 200, and 400 nmol/m in/100 g body weight), taurochenodeoxycholate (25, 50, 100, and 200 nm ol/min/100 g body weight), tauroursodeoxycholate (100, 200, 400, and 8 00 nmol/min/100 g body weight), or taurobetamuricholate (100, 200, 400 , and 800 nmol. min/100 g body weight). Bile was collected to analyze bile flow, bile acid output, cholesterol levels, and lecithin levels, The hydrophobic-hydrophilic balance of the bile salts and biliary leci thin species was assessed by determining the retention times during re verse-phase high-performance liquid chromatography, Biliary lecithin s ecretion rates correlated with the hydrophobicity index of the biliary bile salts administered. Thus, biliary lecithin hydrophobicity increa sed with increasing bile salt hydrophobicity, whereas the molar choles terol-lecithin ratio in the bile decreased. In conclusion, bile salt h ydrophobicity regulates the selection of biliary lecithin subspecies d uring biliary secretion and thereby modulates, at least in part, bile cholesterol metastability. Thus, bile salt hydrophobicity accounts for the physicochemical conditions determining bile lipid metastability.