Effect of tryptophan and nicotinamide loads on urinary excretion of RNA metabolites by bladder cancer patients.

In a comparative study of tryptophan metabolism and urinary excretion of nucleic acid derivatives (including beta-aminoisobutyric acid, 7-methylguanine, pseudouridine, and urate) in 12 male bladder cancer patients, the excretion of pseudouridine and 7-methylguanine decreased significantly after an oral dose of 2 g L-tryptophan. A similar decrease occurred after an oral nicotinamide load of 50 mg four times a day, which indicated a possible common mode of action of tryptophan and nicotinamide. No definite resolution could be made as to the causal mechanism for the observed descrase in RNA turnover.