Platelet sodium-hydrogen exchanger activity and left ventricular mass

Introduction: The sodium-hydrogen exchanger (NHE) is integral to the proces ses that facilitate cell growth and may contribute to the development of le ft ventricular hypertrophy. The aim of this study was to examine the relati onship between platelet sodium-hydrogen exchanger activity and left ventric ular mass index (LVMI). Methods: Twenty male untreated Caucasians (mean age +/- s.d.: 48 +/- 13; bo dy 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-de pendent recovery of intracellular pH in isolated platelets loaded with BCEC F and acidified to pH 6.25 using nigericin. LVMI was calculated from measur ements made by M-mode echocardiography. Associations between continuous var iables were examined using parametric tests. Results: The mean rate of pHi recovery was 0.15 +/- 0.03 dpHi/s (range: 0.0 9-0.21). Mean LVMI was 120 +/- 32 g/m(2) (range: 56-178) and was not signif icantly correlated with either systolic (r = 0.39, P = 0.09) or diastolic b lood pressure (r = 0.27, P = 0.3). Platelet NHE activity was not significan tly 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 n ot significantly correlated with LVMI. These data contrast with previously described correlations of LVMI with exchanger activity measured in leucocyt es and erythrocytes; and indicate that the relationship between LVMI and ex changer activity may be specific to the cell type in which exchanger activi ty is measured.