Uptake of barbituric acid derivatives in small intestinal brush border membrane vesicles from retinyl palmitate-treated rats

Brush border membrane was prepared from the small intestinal (jejunum) cell s along the crypt-villus axis. The fluorescence spectra of 1,8-anilinonapht halene sulfonic acid and the steady-state fluorescence anisotropy of 1,6-di phenyl-1,3,5-hexatriene were measured in the brush border membrane vesicle suspension. The hydrophobicity of brush border membrane was found to be in the order villus tip >mid villus >lower villus. The fluidity of brush borde r membrane was in the order villus tip <mid villus <lower villus. The uptak e of barbituric acid derivatives by brush border membrane vesicles was well correlated with their partition coefficients (isopentyl acetate/water). No significant difference was observed between the uptake of hexobarbital by brush border membrane vesicles from the villus tip and lower villus. When r etinyl palmitate was administered to rats, the fluidity of brush border mem brane was found to be higher in the retinyl palmitate-treated rats than in the control rats. However, no significant difference in the uptake of hexob arbital by brush border membrane vesicles was observed between the retinyl palmitate-administered rats and the control rats. Thus, the retinyl palmita te treatment seems unlikely to affect the passively transported ligands lik e barbituric acid derivatives in brush border membrane vesicles.