1. Lymphocytes from normotensive subjects with normal intralymphocytic sodium content were incubated for 1 h in plasma from subjects with essential hypertension, secondary hypertension or borderline hypertension, and from normotensive subjects with (genetic) and without (non-genetic) family history of hypertension.
2. Lymphocytes from non-genetic normotensive subjects greatly increase their intralymphocytic sodium content after incubation in plasma (diluted 1:4) of patients with essential hypertension (but not with secondary hypertension), of borderline subjects and of genetic normotensive subjects with abnormally high intralymphocytic sodium content (<26 mmol/kg).
3. When plasma is diluted 1:8, an increase in intralymphocytic sodium content is detectable only after incubation in plasma of borderline subjects and of genetic normotensive subjects with high intralymphocytic sodium content.
4. These data suggest that a plasma factor altering Na+ transport is detectable in all the subjects in whom intralymphocytic sodium content is high, independently of their blood pressure values. The concentration (or the activity) of this substance is greater in borderline and genetic normotensive subjects than in patients with sustained essential hypertension. This suggests that these subjects are in a dynamic phase of the development of hypertension.