1. Previous histological studies have demonstrated partial reinnervation of the human transplanted kidney. However, it remains unknown whether this reinnervation is of any functional significance.
2. The effects of noradrenaline infusion (2 μgh−1kg−1) and lower body negative pressure (−27 mmHg) on renal haemodynamics, sodium excretion and tubular function were investigated in 25 renal transplant recipients and 10 normal subjects. Sixteen of the transplant recipients had all been transplanted for more than 27 months, and nine had all been transplanted for less than 2 months.
3. After an overnight fast, the subjects were water-loaded, and clearance studies were performed with a 1 h baseline period, a 1 h period with noradrenaline infusion, another 1 h baseline period, and a final 1 h period with lower body negative pressure.
4. During noradrenaline infusion the relative decrease in effective renal plasma flow, glomerular filtration rate and clearance of lithium and sodium was significantly more pronounced in the long-term transplanted patients than in the control subjects.
5. Lower body negative pressure only depressed the glomerular filtration rate significantly in the control subjects. Further, the relative decrease in effective renal plasma flow and clearance of lithium and sodium was significantly greater in the control subjects than in the two groups of transplanted patients.
6. The present study thus demonstrated that in short- and long-term transplanted kidneys in man, supersensitivity to circulating noradrenaline and an inadequate response to lower body negative pressure was present. This strongly suggests that the human transplanted kidney remains functionally denervated.