We examined bile acid transport and expression of the apical sodium-dependent bile acid transporter (ASBT) in ileal preparations to determine if alterations in bile acid excretion contributed to a hypercholesterolemia-resistant phenotype in rabbits (CRT/mlo). Taurocholate transport was not different between normal (NR) and CRT/mlo rabbits fed regular diet. However, feeding cholesterol-enriched diet reduced taurocholate transport significantly in CRT/mlo rabbits (0.53 + or - 0.06 pmol/microg protein) compared to regular diet (0.95 + or - 0.14 pmol/microg protein), but had no effect in NR rabbits. Cholesterol-enriched diet increased ASBT mRNA in CRT/mlo (2.6 + or - 0.7 to 5.4 + or - 0.1); no significant changes occurred in NR. Some CRT/mlo rabbits carry a polymorphism in ASBT at amino acid 333 (P333L). In transfected HEK293 cells, TC transport of P333L allele was significantly lower (0.08 + or - 0.01 vs 0.13 + or - 0.01 pmol/microg protein/15 sec, P< 0.05). This allele was not found in NR rabbits. The data suggest that the phenotype of the CRT/mlo rabbit is due to changes in bile acid transport as well as bile acid metabolism.