Impaired response of plasma renin activity to tilting after renal transplantation

Studies on the innervation of human renal allografts

Kidneys are innervated by a plexus of nerves around the renal artery, which is disrupted by transplantation. This is a report of a comparison of the nerves in human renal allografts and normal kidneys. There were many sympathetic ganglia around normal renal arteries but none around transplanted vessels, although equal numbers of ganglia were present in hilar tissues of normal and transplanted kidneys. An immunohistological study with an antibody to synaptophysin showed that the number of synapses in transplanted ganglia was severely reduced. Immunohistological studies on allograft kidneys using antibodies to various neurofilament proteins and the Schwann cell marker S100 showed a marked reduction in neurofilament proteins shortly after transplantation with subsequent partial recovery, and a lesser reduction in S100. Renal allografts have structurally abnormal innervation but are not completely denervated.

[Sympathetic activity in terminal renal failure and kidney transplants]

Blood pressure as well as noradrenaline, creatinine and electrolytes in blood and urine were compared in normal controls (n = 25), patients with chronic renal failure (n = 39), patients with continuous ambulatory peritoneal dialysis (CAPD) (n = 28) and haemodialysis patients before and after renal transplantation (n = 63). The average blood pressures of the control group and the CAPD patients were lower than those of the renal failure patients without and with haemodialysis. After renal transplantation elevated blood pressure normalised in 18% within the following 6 months. In all groups of patients with renal failure the mean noradrenaline plasma concentration was increased more than three-fold of normal values: 1,470 pg/ml in patients with chronic renal failure, 1,366 pg/ml in CAPD patients and 1,284 pg/ml in patients with haemodialysis. No correlation was found between these elevated noradrenaline plasma levels and blood pressure. However, there was a significant correlation between noradrenaline excretion and sodium excretion. Compared to the controls, the urine excretion of noradrenaline was significantly lower in patients with chronic renal failure and almost zero in patients with dialysis treatment. Two days after renal transplantation the mean noradrenaline urine excretion increased to 15.7 +/- 1.8 micrograms/day and 4 days after transplantation the noradrenaline plasma concentration decreased to 592 +/- 155 pg/ml. Nine months after renal transplantation the creatinine clearance was 76 ml/min and the mean noradrenaline plasma concentration 438 +/- 153 pg/ml. It is concluded that in chronic renal failure the level of noradrenaline plasma concentration is dependent on renal function.

Plasma volumes, noradrenaline levels and renin activity during posture changes in end-stage renal failure

In nine normal subjects and nine patients with end-stage chronic renal failure (CRF) we studied the effect of prolonged (110 min) postural changes on the plasma volume, intrathoracic volume, plasma noradrenaline concentration, haemodynamic variables, and plasma renin activity (PRA). Upon standing, plasma volume decreased rapidly by about 11% in both groups as measured from the control volume and changes in haematocrit. This was accompanied by identical increments of plasma colloid osmotic pressure. The changes in intrathoracic volume (monitored by measurement of the electrical impedance of the thorax), as well as the alterations in plasma noradrenaline, blood pressure, and heart rate, were also comparable in the two groups. These similarities were in contrast with divergent responses of PRA. The increase in PRA on standing was significantly blunted in the CRF patients compared with the normal response (to 1.4 +/- 0.4 fold of the supine value in CRF v. 6.0 +/- 3.2 fold in the normals, P less than 0.0004). It is concluded that the attenuated increase in PRA upon standing in patients with CRF is not a consequence of diminished sympathetic stimulation or an altered response of the intravascular volume. Second, the unabated decrease in plasma volume upon standing pleads against a decrease of tissue compliance in CRF.

Bopindolol: a new long acting beta-receptor antagonist; its effects on haemodynamics, and on the renin response to tilting

Oral administration of single doses of bopindolol (1-4mg) caused significant reductions in the rises of systolic blood pressure and heart rate produced by exercise; only the reduction in the rise of heart rate was significantly dose-related. Resting heart rate was reduced by bopindolol. There were small effects on resting blood pressure. Bopindolol caused a significant attenuation of the rise in plasma renin activity produced by passive head-up tilting to 75-85 degrees. Bopindolol produced a dose-related attenuation of the increase in pulse rate evoked by passive tilting. All effects 1-4 were maintained for at least 24 h. There was no measurable effect on plasma potassium concentration, peak flow rate or forced expiratory volume (FEV1).