Effect of simultaneous thiamin and riboflavin deficiencies on the determination of transketolase and glutathione reductase.

Thiamin and/or riboflavin status have been assessed in rats simultaneously deprived of both vitamins and subsequently repleated with either one or the other in succession. Undernutrition in control rats was found to depress the activity of the erythrocyte enzymes (transketolase and glutathione reductase, respectively) used to assess status. On the other hand, the activity coefficients obtained by in vitro stimulation of the enzymes with their respective missing cofactors were not suppressed. Therefore the activity coefficients were superior indices of thiamin and riboflavin nutriture compared to the enzyme activities. When activity coefficients were used as the indices of vitamin status there did not appear to be interference from the simultaneous deficiency of the alternate vitamin. Apparent interference was encountered when the enzyme activity itself was used as the criteria.