Cellular accumulation of tetrahydrobiopterin following its administration is mediated by two different processes; direct uptake and indirect uptake mediated by a methotrexate-sensitive process
Keywords: Tetrahydrobiopterin; Dihydrobiopterin; Methotrexate; Dihydrofolate reductase; Caco-2 cell; Intestinal epithelium; Hepatocyte; BH4 supplementation;