Japanese individuals do not harbor the T594M mutation but do have the P592S mutation in the C-terminus of the β-subunit of the epithelial sodium channel: The Ohasama Study

Objective: To assess the implications of polymorphisms of the amiloride-sensitive epithelial sodium channel in essential hypertension in the Japanese population by determining the incidence of the T594M mutation in the β subunit of the epithelial sodium channel, and by screening the C-terminus of the epithelial sodium channel. Methods: Single-strand confirmational polymorphism (SSCP) analysis using two sets of primers which cover the last two-thirds of the last exon coding the B epithelial sodium channel and modification of a specific enzyme restriction site (NlaIII) for the T594M mutation were performed on 803 Japanese subjects. They were randomly selected from the study participants representative of a general population of Ohasama, Japan, who measured their home blood pressure. Polymerase chain reaction (PCR) products presenting a shift in SSCP gel, as well as controls, were directly sequenced by autoanalyser to identify the mutation. Results: SSCP analysis identified altered migration in five subjects. Four SSCP variants found by sequencing were heterogeneous for the P592S (CCT to TCT) mutation conserving the PY motif, although it was not significantly associated with either home or casual blood pressure values. The resting polymorphism was at codon Thr 594, leading to no change in the amino acid sequence (ACG to ACA). None of the PCR products were modified by NlaIII, indicating the absence of the T594M mutation. Conclusions: The epithelial sodium channel variants at the C-terminus are not involved in the common form of essential hypertension in Japanese. (C) Lippincott Williams and Wilkins.