Supine and Standing Plasma Catecholamines in Essential Hypertensive Patients with Different Renin Levels

In this study we measured plasma renin activity (PRA), plasma norepinephrine (NE) and epinephrine (E), heart rate (HR) and blood pressure (BP) in 89 supine (sup) essential hypertensive patients (pts), WHO I-II, after 3-5 days of fixed normal sodium and potassium intake; the same measurements were repeated after 30' of active standing (stand) in 44/89 pts. In the whole population NE was directly related to PRA, both in sup and in stand position (p less than 0.01). NE was above the upper limits of normotensive controls in 2/34 (6%) pts with low PRA, in 6/40 (17%) pts with normal PRA and in 6/15 (40%) pts with high PRA. In respect to normal PRA pts, HR was significantly lower in low PRA pts and higher in high PRA pts, both in sup and in stand position (p less than 0.05). Sup and stand NE and E were similar in low and normal PRA pts, while they were significantly higher in high PRA pts (p less than 0.05). These results suggest an increased adrenergic tone at least in some high PRA pts, and blunted responsiveness of renal and cardiac beta adrenergic receptors to adrenergic stimuli in low PRA pts.