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KAROLINA KĘDZIERSKA


ACTIVITY OF THE SODIUM-PROTON EXCHANGER AND POLYMORPHISM
OF G-PROTEIN BETA-3 SUBUNIT IN PATIENTS WITH ESSENTIAL
HYPERTENSION

Summary
The aim of the study was to verify the hypothesis that C825T polymorphism of G-protein β3 subunit is involved in the development of the intermediate phenotype (increased sodium-proton exchanger activity). If true, increased sodium-proton exchange in the proximal tubule would enhance total sodium load and volemia (volumetric component of blood pressure). On the other hand, direct activation of the sodium-proton exchanger in vascular smooth muscle cells would augment vascular tone and eventually lead to hypertrophy of the vascular media and increased resistance (resistance component of blood pressure). Salt sensitivity was confirmed in 54% of patients with hypertension and 26% of controls. Signi.cantly higher activity of erythrocyte and platelet NHE was found in patients with hypertension as compared to controls. The activity of erythrocyte NHE was within normal limits in 59% of patients with hypertension and was increased in the remaining 41%. The activity of platelet NHE was normal in 50% of patients with hypertension and was increased in the remaining 50%. No differences were found in the activities of erythrocyte and thrombocyte NHE between salt-sensitive and saltresistant patients in the hypertension and control groups. Significantly higher activities of erythrocyte NHE were observed in salt-sensitive patients as compared to salt-sensitive controls. Significantly higher activities of erythrocyte and platelet NHE were found in salt-resistant patients as compared to salt-resistant controls. No relationship was found between GNB3 C825T genotypes and salt sensitivity. The frequency of CT+TT genotypes was significantly lower in controls as compared to patients with hypertension. A significantly higher frequency of the T allele was also observed in patients with hypertension as compared to controls. No influence of GNB3 genotypes or T allele on the activity of erythrocyte and platelet NHE, birth weight, BMI, plasma renin activity, aldosterone level, plasma lipid profile, urine and electrolyte excretion was found in patients with hypertension and in controls. The following conclusions were drawn: 1. Increased activity of the sodium-proton exchanger in erythrocytes and thrombocytes was associated with essential hypertension. 2. Activity of the sodium-proton exchanger in erythrocytes and thrombocytes was not a marker of salt-sensitive hypertension in patients on a normal sodium diet. 3. CT+TT genotypes of protein G β3 subunit C825T polymorphism were more frequent in patients with hypertension but were not associated with increased activity of the sodium-proton exchanger in erythrocytes and thrombocytes. 4. CT+TT genotypes of protein G β3 subunit C825T polymorphism were not associated with salt sensitivity in hypertensive patients.


K e y w o r d s : hypertension – sodium-proton exchanger – erythrocyte – thrombocyte – genes – polymorphism – G protein. 

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