Molecular variants of the sodium/hydrogen exchanger type 3 gene and essential hypertension

The objectives of this study were to identify polymorphic variants within the gene coding for the sodium/hydrogen exchanger type 3 (NHE3) and to examine their relationship with hypertension and biochemical indices of sodium balance.

Case-control comparisons on a total of 691 subjects of which 399 (68% with essential hypertension) were of African or Afro-Caribbean origin (blacks) and 292 (50% with essential hypertension) were of Caucasian origin (whites).

Eight exons of the C terminus of the NHE3 gene were screened systematically. A total of six variants were identified: (G1579A, G1709A, G1867A, C1945T, A2041G and C2405T). Further analyses in relation to essential hypertension and phenotypic characteristics were confined to the more frequent A2041G and the C2405T polymorphisms. The genotype frequencies of the A2041G polymorphism were significantly different between the whites and blacks, with the A allele being more frequent in the white population (0.43 for the whites and 0.14 for the blacks, respectively; P < 0.001). In contrast, there was no significant difference in the C2405T polymorphism between whites and blacks (C allele frequency: 0.86 for the whites and 0.88 for the blacks, respectively). In both the white and the black groups, there were no significant associations between these variants and essential hypertension (P > 0.05) or with serum electrolytes, creatinine or plasma renin activity (PRA) (ANOVA P > 0.05).

These results suggest a high degree of structural conservation of the NHE3 gene; however, the lack of association between these polymorphisms and blood pressure status does not necessarily eliminate the participation of this important sodium/hydrogen exchanger in the pathophysiology of essential hypertension, as we cannot exclude the existence of functionally important genetic variants in other sequences within the NEH3 gene.