CHANGES IN INTRAERYTHROCYTE CONTENT AND TRANSMEMBRANE FLUXES OF SODIUM DURING SALT LOADING IN SUBJECTS WITH AND WITHOUT FAMILY HISTORY OF HYPERTENSION

. We studied 17 young normotensive men with family history of hypertension (H) in two generations (father and grandfather) and 17 age matched control subjects (C) with respect to intraerythrocyte sodium (IeNa), sodium influx, and rate of sodium efflux. The investigation was done during ordinary salt intake and after four week's salt load. H had a significantly higher IeNa (9.5 ± 0.4 mmol/l) compared to C (8.2 ± 0.3 mmol/l), p < 0.01. After salt loading H decreased significantly to 8.1 ± 0.3 mmol/l while C did not change significantly (7.6 ± 0.3 mmol/l). There was no significant difference between H and C in Na influx either on normal or on high salt intake. The rate constant for Na efflux was significantly lower on normal salt intake in H (0.0038 ± 0.0003 vs 0.0050 ± 0.0004 min, p < 0.05). High salt intake increased the efflux rate constant significantly in H (0.0048 ± 0.0003 min-1, p < 0.05), while control subjects showed no difference (0.0053 ± 0.0004 min-1) compared to pre-salt conditions. Our results suggest that young men with heredity for hypertension have a higher intraerythrocyte Na-content secondary to a lower rate of Na efflux. The Na influx did not differ between the two groups probably indicating an unchanged permeability for sodium in subjects with a family history of hypertension.