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 < 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 < 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 < 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.