Tetrahydrobiopterin uptake in supplemental administration: elevation of tissue tetrahydrobiopterin in mice following uptake of the exogenously oxidized product 7,8-dihydrobiopterin and subsequent reduction by an anti-folate-sensitive process.

In order to increase the tissue level of tetrahydrobiopterin (BH4), supplementation with 6R-tetrahydrobiopterin (6RBH4) has been widely employed. In this work, the effectiveness of 6RBH4 was compared with 7,8-dihydrobiopterin (7,8BH2) and sepiapterin by administration to mice. Administration of 6RBH4 was the least effective in elevating tissue BH4 levels in mice while sepiapterin was the best.