Dependence of pyridoxine metabolism on riboflavin status in sickle cell patients.

The relationship between riboflavin and pyridoxine status was studied in 40 patients with sickle cell disease (SCD) and 12 normal children by measuring activation coefficients of erythrocyte glutathione reductase (EGRAC) and aspartate transaminase (ASTAC). Prevalence of riboflavin deficiency was significantly lower in SCD (42.5%) than in control subjects (83%) and there was less pyridoxine deficiency in SCD (10.3%) than control subjects (54.5%). Aspartate transaminase (AST) activities in SCD patients were double those in control subjects. Pyridoxine status of patients, but not of control subjects, was directly affected by riboflavin status as judged from significant correlations between EGRAC and both AST activity and ASTAC. Poor riboflavin status in patients may be restricting availability of pyridoxal phosphate (PLP) due to combined effects of enhanced PLP requirements and effects of poor riboflavin status on the synthesis of PLP by pyridoxine phosphate oxidase (PPO). PPO activity was no different in the two groups.