The epithelial sodium channel (ENaC) is expressed in vascular endothelium. Depending on ambient sodium concentration, ENaC mediates mechanical stiffening of the endothelial cell cortex finally leading to endothelial dysfunction. As the incidence of both endothelial dysfunction and salt sensitivity increases with age, we investigated the abundance of endothelial ENaC in ageing mice. To assess ENaC functionality and endothelial cell function, endothelial stiffness was measured while ambient sodium was varied.

Aortae ex vivo of young (3 months) and old (15 months) C57BL/6J mice were kept in culture for 48 hours in the presence of aldosterone (0.45 nM). Spironolactone (10 nM) and amiloride (1µM) were applied for aldosterone receptor and ENaC block, respectively. ENaC at the cell surface was quantified by immunofluorescence staining. Cortical stiffness was measured by atomic force microscopy when ambient sodium was raised from 130 (“baseline”) to 150 (“high”) mmol/l.

In ex vivo aortae of old mice, endothelial cells exhibited significantly higher ENaC numbers than in young ones (14.8 vs. 12.0/1000 µm² cell surface area). In parallel, baseline stiffness was higher (1.38 vs. 1.23 pN/nm). High sodium led to an increase in stiffness in both age groups. Spironolactone and amiloride lowered ENaC abundance and prevented endothelial stiffening at both sodium concentrations.

In summary, the number of endothelial ENaC and endothelial cell stiffness increase with age. Endothelial salt sensitivity is reduced in the presence of spironolactone and amiloride. These results suggest spironolactone and amiloride for the treatment of endothelial dysfunction and cardiovascular disease specifically in the elderly.