1. Intra-arterial pressure, cardiac output, renal blood flow and glomerular filtration rate were measured in 19 patients with low-renin hypertension and in 30 patients with normal-renin hypertension.
2. Cardiac output and renal blood flow were significantly lower in low-renin hypertension. Total peripheral and renal vascular resistance were markedly higher in this group.
3. Plasma renin concentration correlated inversely with both total peripheral and renal vascular resistance as well as with age. Multiple regression analysis indicated that part of the relationship between renin and haemodynamic variables did not depend on age. Furthermore, plasma renin concentration did not decrease with age in a group of 40 normotensive control subjects of similar age to the hypertensive patients.
4. The results provide further confirmation that renin decreases as hypertension progresses.