1. Plasma levels of endothelin were measured in 30 patients with chronic renal failure, 32 patients on chronic haemodialysis treatment and 25 renal graft recipients with stable renal graft function. 2. In patients with chronic renal failure as well as in patients on regular haemodialysis treatment, mean plasma levels of endothelin were significantly increased (4.59 +/- 2.09 pg/ml, 10.08 +/- 3.12 pg/ml, respectively) when compared with normal subjects (1.88 +/- 0.6 pg/ml, P less than 0.01, P less than 0.001, respectively). 3. In the group with chronic renal failure a positive correlation between the plasma level of endothelin and the plasma concentration of creatinine was observed (P less than 0.003). 4. Renal graft recipients on cyclosporin A with stable renal graft function had a normal plasma level of endothelin suggesting that cyclosporin A nephrotoxicity is not mediated by endothelin. 5. Hypertensive patients with chronic renal failure or on regular haemodialysis and hypertensive renal graft recipients did not differ from the corresponding normotensive population with regard to the plasma level of endothelin, demonstrating that an increased plasma level of endothelin does not play a major role in the pathogenesis of renal hypertension.

The elimination of intravenously infused amino acids was evaluated in six patients with acute renal failure (ARF), 6 with conservatively treated chronic renal failure (CRF), 6 subjects receiving regular hemodialysis treatment (RDT), and 5 healthy control subjects. In ARF, CRF, and RDT groups, whole-body clearance (Cltot) of the 10 amino acids was elevated (113.5 +/- 1.5; 94.2 +/- 1.5 and 127.6 +/- 12.4, respectively, vs 85.2 +/- 4.8 mL.kg-1.min-1 in control subjects, P < 0.001). In ARF, Cltot of histidine, lysine, and methionine was higher and Cltot of phenylalanine and valine was lower as compared with control subjects. In CRF, Cltot of tryptophan and histidine was elevated and Cltot of phenylalanine was reduced; in RDT, Cltot of histidine, methionine, tryptophan, lysine, isoleucine, and leucine was raised. In all groups the relative clearance (% of total clearance) of phenylalanine and valine was reduced, and relative clearance of histidine and tryptophan was elevated. We conclude that in renal failure the elimination of amino acids from the intravascular space is profoundly altered and that the pattern of metabolic aberrations is similar in ARF, CRF, and RDT groups.

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Carotid surgery is frequently associated with postoperative blood pressure alterations. The role of baroreceptors with regard to these alterations was assessed in 50 patients by determining the pre- and postoperative mechanoreceptor sensitivity after Valsalva maneuver and intravenous injections of angiotensin and nitroglycerine as described by Smyth, Sleight and Pickering. In addition, blood pressure was monitored perioperatively and renin and aldosterone levels were measured. In patients with arterial hypertension a postoperative increase of receptor reactivity can be seen necessitating a reduction of antihypertensive therapy in more than 50% of cases. In normotensive patients no uniform response can be observed. A possible explanation for this effect might be the local increase of pressure in the operated vascular segment. The postoperative reintegration of receptor areas which had been adjusted to a reduced pressure level might induce a more sensitive response than can be seen for the remaining receptors, which usually are less responsive in hypertensive patients.