Background. The role of nitric oxide (NO) after cadaveric renal graft transplantation has not been yet fully clarified. The aim of our study was to examine NO production into the urine of patients following cadaveric renal graft transplantation with a normal course and complications (acute rejection and cyclosporin toxicity). Methods and Results. Production of stabile NO metabolites (NO 2 - and NO 3 - ) into urine (U-NOx) was examined in recipients of cadaveric renal transplantation. Only patients with standard triple immunosuppressive therapy (cyclosporin, azathioprine, prednisone) were include into the study. Patients receiving other immunosuppressive agents or drugs affecting NO formation (nitrates, ACE inhibitors) were excluded from the study, as were those with infectious or other serious post-transplant complications. Overall, we examined 33 patients (21 men and 12 women), with acute rejection and cyclosporin-induced toxicity in ten each, and a normal course with no complications in 13. The mean age of the patients was 50.96 _ 11.13 years. U-NOx was examined by biochemistry using Griesse reaction every day after transplantation both in a morning urine sample and in a sample from 24-hour collection over the preceding day and calculated to 1 mmol/l of urinary creatinine (U-Cr). The levels of U-NOx/U-Cr in patients with acute rejection over the past 2 days before its development were lower compared with those in patients with a normal course (p_0.05). No difference was found between the groups of patients with cyclosporin-induced toxicity and a normal course. The levels of U-NOx were inversely correlated (p_0.01) to the levels of serum creatinine (S-Cr), but did not correlate with the blood levels of cyclosporin A. Conclusions.The study demonstrated a decrease in urinary U-NOx production within the past 2 days before renal transplant rejection. The levels of U-NOx in patients with cyclosporin-induced toxicity remain unaltered. U-NOx/U- Cr could possibly become a non-invasive marker of rejection.

        Key words: NO, cyclosporin, renal transplantation, acute rejection, cyclosporin-induced toxicity.