1. Erythrocyte lithium—sodium counter-transport was measured in 46 normotensive healthy controls without family history of hypertension, 15 subjects with essential hypertension, but without evidence of family history of high blood pressure, and 43 subjects with essential hypertension and at least one hypertensive first-degree relative.
2. Mean values (mmol h−1 l−1 of erythrocytes) were 0.248 ± 0.092 in controls, 0.258 ± 0.087 in hypertensive subjects without family history (not significant vs controls), 0.360 ± 0.115 in hypertensive subjects with family history of hypertension (P < 0.001 vs controls), 0.334 ± 0.117 in all hypertensive subjects, both with and without family history (P < 0.001 vs controls).
3. Our data confirm the finding of an increased erythrocyte lithium-sodium counter-transport, but with a significant overlap between essential hypertension and control values. Lithium-sodium countertransport is higher only in hypertensive subjects with at least one hypertensive first-degree relative.
4. We suggest that the increase of lithium-sodium countertransport in erythrocytes is not a consistent marker of essential hypertension. It seems to be associated with the family prevalence and/or the hereditability of hypertension, rather than with high blood pressure per se.