G-protein β3-subunit gene variant, blood pressure and erythrocyte sodium/lithium countertransport in essential hypertension

Abstract

Recently, a C825T polymorphism in the gene coding for the β3 subunit of G proteins (GNB3) has been described in cells from patients with essential hypertension and enhanced Na⁺/H⁺ exchange activity. This study aims to evaluate the association between the 825T allele and activity of erythrocyte sodium/lithium countertransport (Na⁺/Li⁺ CT) and other sodium transport systems in red blood cells from patients with essential hypertension. A group of 77 patients (36 male, 41 female; aged 51.7 ± 1.1 years) was studied. The maximal rates (V_max) of Na⁺/Li⁺ CT, Na⁺/K⁺/Cl-cotransport and Na⁺K⁺ ATPase were evaluated in erythrocytes from all the patients. They were genotyped for the C825T polymorphism by a polymerase chain reaction (PCR) method, followed by digestion with BseDI. Body mass index (BMI) was higher in CT+TT patients than in CC patients (28.9 ± 0.5 vs. 27.0 ± 0.7 kg/m²; P=0.023). Hypertensives with the T allele (CT+TT genotypes) showed significantly higher systolic blood pressure (BP) values (156.9 ± 2.1 vs. 148.9 ± 2.8 mmHg; P=0.024), whereas differences in diastolic BP did not reach statistical significance (96.4 ± 1.0 vs. 94.0 ± 1.1 mmHg; P=0.120). No differences in the V_max of Na⁺/Li⁺ CT between the genotypes was seen (CC: 236 ± 19 and CT+TT 277 ± 23 mmol/L cells per h; P=0.221). Similarly, no differences were detected in the V_max of erythrocyte Na⁺/K⁺/Cl-cotransport and Na⁺K⁺ ATPase among the genotypes. There was no appreciable association between the G-protein β3-subunit C825T polymorphism and erythrocyte Na⁺/Li⁺ CT and other sodium transport systems in the hypertensive patient sample studied; however, those with the T allele were more obese and had more severe systolic hypertension.

Keywords:

• GTP-binding proteins
• Hypertension
• Lithium
• Obesity
• Polymorphism (genetics)
• Sodium