[Catecholamine content of adrenergic nerves in salivary glands with pathological electrolyte pattern in uremia. A fluorescence and enzyme histochemical study (author's transl)]

Haemodynamic effects of prenalterol in patients on dialysis

Haemodialysis hypotension occurs with particular frequency in bilateral nephrectomised patients. This reflects the importance of the renin-angiotensin-aldosterone system for maintaining normal blood pressure. Failure of vascular access (due to clotting and thrombosis of shunts) and ischaemic necrosis of transplanted kidneys in hypotensive patients prompted us to treat them orally with a new beta 1-adrenergic agent (prenalterol). Blood pressure was normalised in 4 out of 5 patients. Because of delayed renal elimination of the drug, daily dosage must be reduced to prevent symptoms of adrenergic stimulation. A study of the pharmacokinetics of prenalterol in uraemia is in preparation.

Noradrenaline turnover in the tissues of uraemic rats

In female Wistar rats with acute renal failure a decrease of noradrenaline concentration in the heart, spleen and kidney was ascertained. Noradrenaline concentration after alpha-methyl-p-tyrosine and 6-hydroxydopamine in the heart, spleen and kidney was significantly lower than in the control group. In the adrenals a decrease of catecholamine level after alpha-methyl-p-tyrosine and 6-hydroxydopamine has been noted in the controls. The changes in tissue noradrenaline concentration are evidence of a dysfunction in the adrenergic nervous system in uraemic rats.

Plasma and brain catecholamines in experimental uremia: acute and chronic studies

To evaluate the role of catecholamines (CA) in uremia, we used "high performance" liquid chromatographic technique with electrodetection to determine plasma and brain concentration of dopamine (DA), norepinephrine (NE) and epinephrine (E) in rats with acute and chronic uremia. The results revealed a steady elevation in plasma CA (p less than 0.05) in both acutely and chronically uremic rats when compared to the level of these neurotransmitters in controls. The highest changes were observed in DA and the least in NE (16.8 +/- 3.2 vs. 0.5 +/- 0.2 ng/ml and 93.2 +/- 11.1 vs. 68.1 +/- 16.3 ng/ml). There was a positive correlation between plasma CA and the duration of uremia (r = 0.97; p less than 0.05). The elevations were more pronounced in acutely uremic rats than in chronically uremic rats. This was followed by a concomitant depletion in the concentration of DA, NE and E in the brain. The defects in catecholaminergic neurotransmission as evidence of dysfunction in the autonomic nervous system may contribute to the development of neuropathy.

Uraemic sympathetic neuropathy after haemodialysis and transplantation

Autonomic function in patients with uraemia treated conservatively, by haemodialysis, and by transplantation was evaluated by the pupillary reaction to tyramine, the Valsalva manoeuvre and a postural tolerance test. The pupillary reaction to tyramine is diminished in haemodialysis patients compared with control subjects. Renal transplantation improves, but does not correct the pupillary reaction to tyramine. The frequency of the diminished response roughly correlates with the degree of renal insufficiency, with results of a Valsalva manoeuvre, and with postural tolerance tests. Our data show that uraemic autonomic dysfunction is improved by successful renal transplantation, but not by adequate haemodialysis.

[Dopamin-beta-hydroxylaseaktivität im Plasma von Dialysepatienten (author's transl)]

Plasma dopamin-b-hydroxylase (DBH) was studied in 70 healthy control persons and in 37 hemodialysed patients. Basal DBH in controls corresponded to 50.0 +/- 29.3 IU. There was was no significant difference between males (53.9 +/1 33.8 IU) and females (47.4 +/- 25 IU); no correlation could be found between age and plasma DBH. In hemodialysed patients basal DBH levels were significantly (p less than 0.01) decreased (32.5 %/- 17.6 IU), suggesting lowered sympathetic activity and/or abnormalities in release, distribution space, or metabolism of DBH. During hemodialysis plasma DBH activity rose during ultrafiltration. This finding indicates a directionally appropriate sympathetic reflex response to volume depletion in dialysed patients.

[Pupillary reaction on tyramine- a parameter of uremic sympathicopathy (author's transl)]

Clinical tests, for instance pupillometry, Valsalvatest, and orthostatic tests show evidence of sympathicopathy in chronic renal failure (GFR: less than 30 ml/min). Hemodialysis does not improve the intensity or frequency of the alterations. Toxic effects of uremic toxins on the autonomic nervous system can be supposed.