[On the fluctuation of plasma biopterin levels for 24 h in normal controls]

Tetrahydrobiopterin (BPH4) is the cofactor for the pteridine-dependent monooxygenases, which play important roles in the biosynthesis of cateholamines and indolamines. These biogenic amines have been thought to be related to affective disorders, and the increase of total biopterin (BP) and the lower ratio of BPH4 to total BP were observed in plasma of patients with affective disorders. For the purpose of giving an explanation of these changes of plasma biopterin mentioned above in patients with affective disorders, the fluctuation of plasma biopterin levels for 24 h was measured by high-performance liquid chromatography with fluorescence detection by the method of Fukushima and Nixon in ten normal volunteers. The total BP and BPH4 levels in plasma at 9 am were the highest, and those levels at 1 am were the lowest. The range of the fluctuation of total BP with the passage of time was narrow compared with the range of the increase of total BP observed in the patients with affective disorders. Other factors in addition to the fluctuation of plasma BP for 24 h were thought to be related to the changes of plarma BP levels in the patients with affective disorders.