1. Relationships between labelled albumin disappearance rate (LADR), plasma volume, blood volume, plasma renin activity (PRA) and blood pressure (BP) were studied in normotensive control subjects and patients with hypertension of different aetiology and severity. In essential hypertensive patients without complications an inverse linear relationship was found between blood pressure and plasma or blood volume.
2. Very close inverse correlations were found between LADR and PRA in both normotensive subjects and patients with uncomplicated essential hypertension. LADR appears to be an excellent reference standard for PRA.
3. It is postulated that LADR mainly reflects the relation between circulating fluid and vascular capacitance tone. LADR is increased in hypertension and blood volume may still be inappropriately high.