The role of the adrenergic system in hypertension after renal transplantation.

Heart rate and blood pressure responses to head up tilt in renal transplant recipients were the same as in normal subjects. Resting plasma noradrenaline was higher in transplantees compared to normal subjects but did not differ between normotensive and hypertensive patients. Plasma noradrenaline rose normally in normotensive patients but did not rise in hypertensive patients in responses to head up tilt. The rise in blood pressure during noradrenaline infusion was significantly greater in hypertensive than in normotensive transplantees. The responses to infused isoprenaline were the same in both groups. Total exchangeable sodium was significantly greater in hypertensive than in normotensive patients. Extracellular fluid volume expansion associated with increased alpha receptor sensitivity to noradrenaline may cause hypertension in renal transplant recipients.