Background. The aim of the study was to examine the role of endothelin in radiocontrast-induced nephropathy (RCN) in patients with chronic renal failure. Methods. We measured plasma endothelin-1.(ET) and the urinary excretion of endothelin-like immunoreactivity before and after infusion of radio contrast medium (CM) in patients with normal renal function (group N; n = 6; mean serum creatinine concentration, 0.8 ± 0.1 (SEM) mg/dl), and in another group, with renal dysfunction (group R; n = 6; 2.7 ± 0.5 mg/dl). Half-normal saline (0.45% NaCl solution) was continuously infused in all patients for 25 h, at a rate of 100 ml/h; starting from 5 h before the infusion of CM. Results. Plasma ET in group R (5.2 ± 1.4 pg/ml) was significantly higher than in group N (0.9 ± 0.3; P < 0.01). Urinary endothelin excretion corrected by creatinine concentration (uET/Cr) in group R (7.9 ± 2.4 mg/g Cr) was significantly higher than in group N (1.5 ± 0. 4 mg/g Cr; P < 0.05). Urinary excretion levels of N-acetyl-β -D-glucosaminidase (NAG) and β2-microglobulin (β2M) were also significantly higher in group R (0.8 ± 0.2 mU/g Cr and 670 ± 400 mg/g Cr, respectively) than in group N (0.3 ± 0.1 and 7.5 ± 2.2, respectively). After CM infusion, uET/Cr in group R significantly increased, to 10.7 ± 2.6 mg/g Cr on the next day and returned to baseline level on the third day. NAG and β2M showed a similar pattern, but a significant change in NAG was observed on the second day in group R. In group N, uET/Cr, NAG, and β2M did not change after CM infusion. Plasma ET remained unchanged throughout the observation period of 4 days in both groups. No patient developed pulmonary edema or a significant rise in serum creatinine (more than 0.5 mg/dl), caused by infusion of the amount of half-normal saline used. Conclusions. In the present study, uET/Cr increased after the administration of CM only in the patients with renal impairment. This difference in endothelin reaction may be a causal one, in that patients with renal insufficiency readily develop RCN. The infusion of half-normal saline starting before CM infusion causes no side effects and is safe for the prevention of CM-induced acute renal failure.
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