NADH-METHEMOGLOBIN REDUCTASE (CYTOCHROME B(5) REDUCTASE) LEVELS IN 2 GROUPS OF AMERICAN BLACKS AND WHITES

Background: Sickle cell trait, glucose-6-phosphate dehydrogenase (G6PD ) deficiency and alpha-thalassemia trait are common genetic abnormalit ies among the American Black population, Under oxidative stress, the p resence of any of these conditions would predispose the hemoglobin (Hb ) to oxidation resulting in accelerated methemoglobin (metHb) formatio n, It was hypothesized that red cells phenotypic for these genetic var iants should have more or different levels of metHb reductase (cytochr ome b(5) reductase) activity. Methods: To test this hypothesis, we mea sured the red cell metHb reductase activity in 558 male subjects (316 Blacks and 242 Whites), by the procedure described by Beutler, All Bla ck patients also had G6PD spot test and Hb electrophoresis, In additio n, all patients had a complete blood count (CBC), If the hematocrit wa s < 35% a reticulocyte count was also done, Patients with corrected re ticulocyte (retic count x hematocrit/45) index over 2% were excluded r egardless of other findings. Results: The results shelved that Blacks had different metHb reductase activity levels than Whites (mean = 3.19 vs 2.89 IU/gHb, respectively with p = 0.03), However, the differences in metHb reductase activities in patients with sickle cell trait, G6P D deficiency, and low MCV < 80 mu(3) (presumptively having a-thalassem ia) in small subgroups did not reach statistical significance (p = 0.2 ), although, all 3 groups were comprised of small numbers. Conclusions : It is concluded that American Blacks have significantly different me tHb reductase activity, The different metHb reductase activity in Blac ks seems to be unrelated to the presence of G6PD deficiency, sickle ce ll trait, or a-thalassemia and it may be the result of genetic polymor phism, However, our study samples do not exactly represent the cross-s ections of the Black and White populations, In addition, all patients were male in this study, Therefore, this study should be confirmed usi ng larger and more population-representative samples, The clinical sig nificance of this problem is not clear at this time.