Abstract
A study has been made of the effect of the tubular inhibitor Probenecid on the spontaneous renal excretion of microbiologically determinable thiamine, riboflavin and pantothenic acid in eight rabbits and sixteen humans. Only the excretion of riboflavin was found to the significantly lowered by Probenecid in humans. The decrease in the excretion of thiamine was uncertain, and no significant decrease occurred in the excretion of pantothenic acid per time unit. The mechanisms of the renal excretion of the vitamins and their metabolites are discussed.