Dichotomous development of the organic anion transport protein in liver and choroid plexus

Both adult liver and choroid plexus express the organic aniontransport protein (oatp1) and transport³⁵S]bromosulfophthalein(BSP). Studies of the developing rat liver reveal that oatp1 mRNA andprotein do not begin to be expressed until 15 days postnatal and are atadult levels by 30 days. Uptake of³⁵S]BSP follows thesame time course. In contrast, neonatal rat choroid plexus expressesoatp1 mRNA and protein. When quantified on a weight basis, the uptakeof ³⁵S]BSP in choroidplexus is lower in the adult than at earlier stages of development.Although fluorescence confocal microscopy of adult rat choroid plexusshows that oatp is localized to the apical surface, facing thecerebrospinal fluid, this method reveals an intracellular localizationof oatp1 in the neonate. Approximately 12 wk are required for theappearance of the adult pattern of distribution. Changes in thelocalization and activity of oatp1 during development could play animportant role in the pathobiology of maturation of the liver and thecentral nervous system.