Biotin Transport Through the Blood‐Brain Barrier

Abstract

The unidirectional influx of biotin across cerebral capillaries, the anatomical locus of the blood-brain barrier, was measured with an in situ rat brain perfusion technique employing [³H]biotin. Biotin was transported across the blood-brain barrier by a saturable system with a one-half saturation concentration of ∼ 100 μM. The permeability-surface area products were 10⁻⁴ s⁻¹ with a biotin concentration of 0.02 μM in the perfusate. Probenecid, pantothenic acid, and nonanoic acid but not biocytin or biotin methyles-ter (all 250μM) inhibited biotin transfer through the blood-brain barrier. The isolated rabbit choroid plexus was unable to concentrate [³H]biotin from medium containing 1 nM [³H]biotin. These observations provide evidence that: (1) biotin is transported through the blood-brain barrier by a saturable transport system that depends on a free carboxylic acid group, and (2) the choroid plexus is probably not involved in the transfer of biotin between blood and cerebro-spinal fluid.