Effect of Albumin on the Disappearance of L-Tryptophan from the Perfusate into Isolated Perfused Rat Livers

抄録

In order to clarify the role of albumin in the transport of L-tryptophan (Trp) into the liver, we examined the effect of bovine serum albumin (BSA) on the disappearance of Trp from the perfusate into isolated perfused rat livers. In liver perfusion with the perfusion medium containing 100μM Trp and 0.5, 2, or 4% BSA, the disappearance of Trp from the perfusate was depressed with a decrease in the concentration of free Trp (albumin-unbound form). The perfusion of livers with the medium containing 1mM Trp and 0.5, 2, or 4% BSA had little effect on the disappearance of Trp from the perfusate, though free-Trp concentrations decreased with perfusion time. In the perfusate of liver perfusion with the medium containing 100μM Trp and 0.5% BSA, total Trp concentrations correlated well with free Trp concentrations, whereas when the perfusion medium contained 100μM Trp and 2 or 4% BSA, total Trp concentrations correlated well with bound Trp concentrations. When liver perfusion was conducted with the medium containing 1mM Trp with 0.5, 2, or 4% BSA, there was a good correlation between total Trp and free Trp concentrations in the perfusate. These results suggest that under physiological conditions (ca., 100μM total Trp and 4% albumin), albumin contributes to the maintenance of total serum Trp concentrations and to the constant supply of serum Trp to the liver by lowering changes in free serum Trp concentrations through its binding to the amino acid.