SEASONAL-VARIATION IN SERUM CONCENTRATION OF 5-S-CYSTEINYLDOPA AND 6-HYDROXY-5-METHOXYINDOLE-2-CARBOXYLIC ACID IN HEALTHY JAPANESE

Serum concentrations of 5-S-cysteinyldopa (5-S-CD) and 6-hydroxy-5-met hoxyindole-2-carboxylic acid (6H5MI2C) have been used as biochemical m arkers of melanoma progression. We examined the effect of solar radiat ion on serum levels of 5-S-CD and 6H5MI2C in 10 healthy Japanese by me asuring these markers every month during a period of 2 years. 5-S-CD l evels were higher in early summer and lower in early winter. The diffe rence in the average levels was approximately twofold, but among the 2 40 samples, no individual values exceeded the upper limit of normal va lue, 10 nmol/L. A significant correlation (P<0.02) was observed betwee n 5-S-CD level and solar radiation. 6H5MI2C levels showed a smaller va riation than 5-S-CD. No correlation was observed between 6H5MI2C level and solar radiation. This study showed that serum 5-S-CD and 6H5MI2C in healthy Japanese did not exceed the upper limit of normal values ev en in sunny season.