Platelet sodium-hydrogen exchanger activity and left ventricular mass

Introduction: The sodium-hydrogen exchanger (NHE) is integral to the processes that facilitate cell growth and may contribute to the development of left ventricular hypertrophy. The aim of this study was to examine the relationship between platelet sodium-hydrogen exchanger activity and left ventricular mass index (LVMI). Methods: Twenty male untreated Caucasians (mean age ± s.d.: 48 ± 13; body mass index: 29 ± 4 kg/m 2 ) with a wide range of blood pressures were studied (mean BP: 152 ± 22/93 ± 15 mm Hg; range: 115–190/61–117 mm Hg). Sodium-hydrogen exchanger activity was determined as the rate of sodium-dependent recovery of intracellular pH in isolated platelets loaded with BCECF and acidified to pH 6.25 using nigericin. LVMI was calculated from measurements made by M-mode echocardiography. Associations between continuous variables were examined using parametric tests. Results: The mean rate of pHi recovery was 0.15 ± 0.03 dpHi/s (range: 0.09–0.21). Mean LVMI was 120 ± 32 g/m 2 (range: 56–178) and was not significantly correlated with either systolic ( r = 0.39, P = 0.09) or diastolic blood pressure ( r = 0.27, P = 0.3). Platelet NHE activity was not significantly correlated with LVMI ( r = 0.06; P = 0.8). Platelet NHE activity was not significantly different between subjects with ( n = 7 with LVMI >131 g/m 2 ) and without left ventricular hypertrophy ( n = 13). Conclusions: The results of this study show that platelet NHE activity is not significantly correlated with LVMI. These data contrast with previously described correlations of LVMI with exchanger activity measured in leucocytes and erythrocytes; and indicate that the relationship between LVMI and exchanger activity may be specific to the cell type in which exchanger activity is measured.