Erythrocyte sodium-lithium countertransport in primary and renal hypertension: relation to family history.

Sodium-lithium countertransport (Na-Li CT) has been reported to be increased in essential hypertension (EHT) but the nature and degree of distinction from normal controls in unclear. Of 44 unselected patients with EHT in the hospital hypertension clinic 36% had Na-Li CT greater than the normal control range and 70% of these had a family history of hypertension. Almost all the patients with normal Na-Li CT had no family history of hypertension. Analysis of variance showed that raised Na-Li CT was related to both a family history of hypertension and a family history of a cardiovascular event. Of 23 patients with hypertension secondary to renal disease, 43% had Na-Li CT greater than the normal control range and raised Na-Li CT was related to both a family history of hypertension and a family history of cardiovascular event in the same way as EHT. Raised Na-Li CT was not characteristic of EHT but identified a subgroup of patients with EHT and a family history of hypertension, some of whom also had renal disease.