HLA- and H-2-associated variations of intra- and extracellular magnesium content.

Erythrocyte and plasma magnesium (EMg, PMg) levels have been shown to be genetically controlled in human and mouse. The possible association of these genetic factors with the major histocompatibility complex (MHC) (HLA and H-2) was investigated. Among unrelated adult male blood donors, HLA-B35 carriers have PMg (P less than 0.01) and EMg (P less than 0.0005) levels lower than those of noncarriers, while HLA-B38 carriers exhibit a significant (P less than 0.05) increase of both PMg and EMg levels when compared to the other individuals. Furthermore, HLA identical sibs have EMg values more similar than those of HLA different sibs. In the mouse, erythrocyte (P less than 0.001), plasma (P less than 0.001), liver (P less than 0.03), and spleen (P less than 0.04) Mg contents vary significantly according to H-2, with higher values being found in H-2k than in H-2q or H-2b congenic strains. However, non-MHC genes also have an influence on erythrocyte (P less than 10(-10], plasma (P less than 10(-10], spleen (P less than 10(-5], and kidney (P less than 10(-6] Mg contents as shown by differences between H-2 identical strains, which differ by the C3H and B10 genetic backgrounds. In conclusion, genetic factors controlling intra- and extracellular Mg levels are composed of at least three components: MHC (HLA and H-2)-associated genes, non-MHC genes, and tissue factors modulating the respective importance of the first two sets of factors. The mechanisms underlying this genetic system are discussed.