Post-renal-transplant hypertension Urine volume, free water clearance and plasma concentrations of arginine vasopressin, angiotensin II and aldosterone before and after oral water loading in hypertensive and normotensive renal transplant recipients

Abstract

Urine volume (V), free water clearance (C_H2O) and plasma concentrations of arginine vasopressin (AVP), angiotensin II (A II) and aldosterone (Aldo) were determined before and three times during the first 5 h after an oral water load of 20 ml/kg body wt in 19 patients with post-renal-transplant hypertension (group I), in 13 normotensive renal transplant recipients (group II) and in 20 control subjects (group III). Both V and C C_H2O increased significantly in all groups, but considerably less in groups I and II than in group III. When C C_H2O was related to glomerular filtration rate no differences existed between patients and control subjects. Basal AVP was the same in groups I (3.3 pmol/l, median) and II (3.0 pmol/l), but significantly (p<0.01) higher than in group III (1.9 pmol/1). Basal A II was significantly (p<0.01) elevated in group I (18 pmol/l) when compared to both groups II (10 pmol/l) and III (11 pmol/l), and the level was independent of the presence of native kidneys. Basal Aldo was the same in all groups. During loading, AVP was reduced in all groups, A II was almost unchanged, and Aldo was increased in groups I and II and reduced in group III depending on alterations in serum potassium. Thus urinary diluting ability is reduced in renal transplant recipients due to a reduced glomerular filtration rate. The enhanced A II in hypertensive renal transplant recipients gives further evidence for the point of view that hypertension is angiotensin-dependent in most of these patients.

Key Words:

• aldosterone
• angiotensin II
• blood pressure
• hypertension
• kidney function
• renal transplant recipients
• transplantation
• vasopressin