Pantothenic acid transport and metabolism in the central nervous system

The mechanisms by which pantothenic acid (PA) enters and leaves brain, choroid plexus, and cerebrospinal fluid (CSF) were investigated by injecting [3H]PA either intravenously or intraventricularly into adult rabbits. [3H]PA, either alone or together with unlabeled PA, was infused at a constant rate into conscious rabbits. At 180 min, [3H]PA readily entered CSF, choroid plexus, and brain. In brain, CSF, and plasma, greater than 90% of the 3H was associated with [3H]PA. The addition of 200 mumol/kg PA to the infusion syringe decreased the penetration of [3H]PA into brain and CSF by approximately 70%. Two hours after the intraventricular injection of [3H]PA, [3H]PA was rapidly cleared from the CSF by a probenecid-sensitive mechanism. No metabolism of the [3H]PA occurred in brain. However, 18 h after the intraventricular injection of 37 microCi (34 nmol) of [3H]PA, approximately 40% of the 3H remaining in forebrain was converted to [3H]CoA. These results show that PA enters and leaves CSF and brain by saturable transport systems. However, [3H]PA is very slowly converted to [3H]CoA in brain in vivo.