Plasma atrial natriuretic factor in isolated systolic hypertension in the elderly: response to hypertonic saline infusion.

Plasma immunoreactive atrial natriuretic factor (ANF) and urinary sodium excretion were measured in elderly patients with isolated systolic hypertension (ISH) (n = 11), age-matched essential hypertensive patients (EHT; n = 16) and normotensive subjects (NT; n = 9) before and during a 60 min infusion of hypertonic saline (120 mEq of Na+). An exaggerated natriuresis during the sodium load was observed only in ISH. Baseline plasma ANF levels in ISH were significantly lower (P less than 0.05) than those of EHT and NT. There was no significant change in plasma ANF in EHT and NT subjects after the saline load. In contrast, there was a significant increase in plasma ANF (P less than 0.05) after the saline load in ISH. The change in urinary sodium excretion was significantly correlated with the change in plasma ANF (r = 0.75, P less than 0.01) in ISH. We conclude that an exaggerated natriuresis during a hypertonic saline infusion may be linked to an increase in plasma ANF in elderly ISH patients.