α- and β-Adrenoceptor Blockade Fail to Prevent High Sodium Diet-Induced Left Ventricular Hypertrophy

High sodium diet (HS, 8% NaCl) induces left ventricular hypertrophy (LVH) in normotensive rats without an increase in pressure or volume load or in resting cardiac sympathetic activity. HS may affect LV adrenoceptors density or affinity or their postreceptor pathways, thereby causing LVH. We therefore assessed the effects of HS with and without blockade of alpha1- or beta-adrenoceptors by terazosin or nadolol, alone or in combination, on resting hemodynamics, LV and right ventricular (RV) weights, and LV dimensions of male WKY rats. HS increased LV weight by 14% to 17%, and the ratio of LV wall thickness to radius by 18% to 23%. Singly or in combination, the adrenoceptor antagonists did not prevent HS-induced LVH, but instead aggravated it. The increased ratio of LV wall thickness to radius and of LV to RV were attenuated by terazosin or nadolol alone. Neither the resting LV peak-systolic or end-diastolic pressures nor the right atrial pressure was changed by HS, either alone or in combination with the blockers. The failure of chronic alpha1- or beta-blockade to prevent HS-induced LVH suggests that adrenoceptor activation is not important in evoking the LVH. However, the blockers shifted the LVH from a concentric to an eccentric form, suggesting an involvement of additional trophic factors during adrenoceptor blockade.