Seasonal variation in urinary excretion of 5-S-cysteinyldopa in healthy Japanese.

The urinary excretion of 5-S-cysteinyldopa was examined in 10 healthy Japanese subjects once a month during a period of one year. The mean values were highest in August (296 micrograms/day) and lowest in February (141 micrograms/day). Individual variations were so great that only a weak difference was observed (p less than 0.05).