The Renin‐Aldosterone System and Renal Hemodynamics in Patients with Posttransplant Hypertension

Abstract

Plasma renin concentration (PRC), plasma aldosterone concentration (PAC), renal plasma flow (RPF) and glomerular filtration rate (GFR) were studied in 19 patients who had received a renal allotransplant. Group 1 consisted of 7 normotensive and group 2 of 12 hypertensive patients. Bilateral nephrectomy was performed in all patients; all were on a fixed daily Na intake, and no antihypertensive agents were given. No significant differences were found between the groups in age, time after transplantation or dosages of prednisone. PRC and PAC were normal in all but 1 patient in group 1 and 2 in group 2. In these 3 patients a slight elevation of PRC was measured. After 1 h in the erect position, a significant increase was measured in PAC, but not in PRC in both groups. After 6 days on a 10 meq Na diet, PRC and PAC increased significantly in both groups. After a further 6 days on the diet plus 150 meq Na daily, significant decreases in PRC and PAC were measured in both groups. No differences were detected in PRC or PAC between groups 1 and 2 either before or after the 2 dietary periods. RPF was significantly lower in the hypertensive group, no significant difference was found in GFR between the groups. No significant relationship could be demonstrated between blood pressure (BP) and PRC or PAC, and PRC and PAC were not correlated to each other. RPF was significantly correlated to mean BP and PRC in the normotensive group but not in the hypertensive. PRC and PAC are normal in most patients with posttransplant hypertension, but the RPF is decreased. An abnormal regulation of renin secretion plays a role in the sustained elevation of BP after renal allotransplantation.