1. Twenty young subjects with borderline hypertension were studied to evaluate the effects of moderate salt restriction and/or of a high potassium intake on intralymphocytic sodium content and blood pressure. Blood pressure was measured after 1 min (casual) and after 5 min (baseline) of rest and during handgrip.
2. Moderate sodium restriction (from 170 to 100 mmol of sodium/day) decreased both intralymphocytic sodium content and diastolic blood pressure at rest and during handgrip. During a high potassium diet (130 mmol of potassium/day) both intralymphocytic sodium content and baseline diastolic blood pressure rose significantly whereas casual diastolic blood pressure remained unchanged and pressor response to handgrip was reduced by 50%.
3. The increase in intralymphocytic sodium content induced by the high potassium diet was dose-dependent. A daily dose of 0.8 mmol of potassium/kg body weight produced the maximal protective effect on blood pressure during exercise with minimal effects on intralymphocytic sodium content and baseline blood pressure.
4. In borderline subjects a low sodium/high potassium diet seems to produce the most favourable effect, since intralymphocytic sodium content and baseline blood pressure remain unchanged whereas the pressor response to handgrip is reduced.