The mouse beta globin gene locus (Hbb) differs in inbred C57BL/6J (C57) and 129S1/SvImJ (129) mice such that beta globins produced by 129 mice have a glycine to cysteine substitution at position 13. Because beta globin cysteine residues bind glutathione, we hypothesized that beta globin genotype is an independent modifier of erythrocyte glutathione distribution between bound and free compartments. Blood was collected from ten C57, ten 129, and forty B6129SF2/J (F2) hybrid mice at eight weeks of age. Hemoglobin genotype and glutathionyl hemoglobin (Hb-SSG) levels were determined by capillary isoelectric focusing. The molar concentration of bound glutathione was calculated based on Hb-SSG. Reduced (GSH) and oxidized (GSSG) glutathione were measured by capillary zone electrophoresis. The beta globin genotypes of the F2 hybrid mice were homozygous C57 (F2-C57, n = 10), heterozygous (F2-C57x129, n = 19), and homozygous 129 (F2-129, n = 11). Free glutathione levels (GSH + GSSG, μmol/L RBC) were significantly higher (means ± SEM, p < .01) in C57 (2188 ± 81) and F2-C57 (2247 ± 147) mice compared to F2-C57x129 (1960 ± 53), F2-129 (1921 ± 53), and 129 (1724 ± 75) mice. Hb-SSG levels (% of total Hb) were significantly higher in 129 (10.2 ± 0.4), F2-129 (8.8 ± 0.3), and F2-C57x129 (5.8 ± 0.2) mice compared to C57 (1.2 ± 0.1) and F2-C57 (1.3 ± 0.1) mice. Total erythrocyte glutathione concentration (bound + free) was not significantly different between strains. However, the proportion of bound glutathione was significantly higher in mice homozygous or heterozygous for the 129 beta globin genotype: 129 (20.2 ± 0.8), F2-129 (16.3 ± 0.8), F2-C57x129 (11.3 ± 0.6), F2-C57 (2.5 ± 0.2), and C57 (2.3 ± 0.1). These results show that the distribution of erythrocyte glutathione between bound and free compartments is strongly linked to mouse beta globin genotype, presumably due to the presence of the additional beta globin cysteine residue. We conclude that mouse beta globin genotype is an independent modifier of erythrocyte glutathione metabolism that may influence nitric oxide metabolism, free radical scavenging, and other important functions of glutathione.
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