Effect of sulfite on red blood cell deformability ex vivo and in normal and sulfite oxidase-deficient rats in vivo

The effect of sulfite, a widely used food additive, on red blood cell deformability ex vivo and in vivo was investigated. Ex vivo experiments were conducted in human blood exposed to sulfite (5, 10 and 20 mM). In vivo experiments were carried out in sulfite oxidase-competent (SOXC) and sulfite oxidase-deficient (SOXD) rats. In the in vivo experiments, sulfite was administered in the form of sodium metabisulfite (Na2S2O5, 25 mg/kg/day) via drinking water. Vitamin E dissolved in olive oil at a dose of 50 mg/kg was administered by gastric gavages. Red blood cell (RBC) deformability was determined at various fluid shear stresses using an ektacytometer. Ex vivo sulfite exposure to RBC did not affect RBC deformability. In the in vivo experiments, although RBC deformability was not affected by sulfite treatment in SOXD rats, it was found to be significantly increased in SOXC rats. Vitamin E treatment in combination with sulfite caused impairment in RBC deformability in both SOXC and SOXD rats. We suggest that sulfite needs to be oxidized in order to improve RBC deformability.