Influence of age on the response to increased salt intake: effects on blood pressure and sodium in erythrocytes.

Blood pressure (BP), sodium in erythrocytes (IeNa) and transmembrane sodium fluxes were determined in normotensive 30 and 50-year-old men with a family history of hypertension (group H; n = 17 and 11 respectively) and without such history (group C; n = 15 and 26 respectively) during normal salt intake and after four weeks on ordinary diet plus 12 g NaCl daily. The 50-year-old men showed a significant increase in BP and weight during high salt intake while the younger men did not. On normal salt, group H had a significantly higher IeNa than group C in both age groups. In the younger group this was accompanied by a decreased Na efflux rate constant. IeNa decreased significantly in group H in both age groups. The decrease in IeNa and increase in pump activity in group H during high salt intake does not support the existence of a sodium transport inhibitor. The increase in BP in the older group during high salt indicates that age is an important factor in BP response.