Postural Changes of Plasma Renin Activity after Renal Transplantation

Abstract

1. Postural changes of plasma renin activity (PRA) before and after the administration of a beta-blocking agent (oxprenolol) were studied in nine patients with renal homotransplantation and in ten normal subjects.2. In normal subjects PRA always increased during upright posture without any correlation with postural changes in mean arterial pressure. Oxprenolol reduced the postural increase of PRA.3. A postural increase of PRA could be detected as early as 20-25 days after renal transplantation, and appeared with increasing frequency as time elapsed.4. There was a significant inverse correlation (r = -0.794, P<O.OOl) between the postural changes of PRA and those of mean arterial pressure. 5. These results suggest that in patients with renal homotransplantation the postural increase of PRA can only partly be due to circulating catecholamines or the sympathetic nervous system and may be explained by inverse changes in the mean arterial pressure.

Renin response to stimulation of cardiopulmonary mechanoreceptors in man.

“…Oparil et al (37), using 800 tilt, observed a small increase of renin after 5 min; the increase was highest after 20 min. Similar results were reported by others (38,39). In these studies with the strong stimulus of orthostasis, it took considerable time before large renin changes were ob-served.…”

The Effect of Clonidine on Plasma Renin Activity in Human Hypertension

“…Venous blood was sampled in every case 2 h after the last drug administration. The effect of a P-blocker (oxprenolol) as described by Salvetti et al (1971) and of an ublocker (phentolamine 20 mg per os every 8 h for 1 day) was also investigated respectively in seven and two patients. Body weight, urinary and plasma sodium and potassium concentration (by flame photometry) and blood arterial pressure (by a sphygmomanometer) were monitored daily.…”

Influence of Age and Sodium Intake on Plasma Renin Activity of Normal Subjects

“…In normotensive, normovolemic subjects the main mechanisms controlling renin secretion are represented by sodium [I] and potassium [2] intake and by sympathetic nervous system [3] activity which acts mainly during the upright position [4,5]. Moreover, recent reports have pointed out the fact that age influences renin, both in ani mals [6] and hypertensive subjects [7,8], However, when normotensive subjects are considered some discrepancies arise since some reports indicate the presence of this in fluence [9,10], and others do not find it [8.11,12].…”