Experiments were designed to investigate whether there is any correlation between concentration of plasma nitric oxide and pathological severity of acute rejection after lung allograft.

After single lung allograft, dogs were immunosuppressed with triple standard therapy and divided into 2 groups. Group 1(Immunosuppression ; n=4) was maintained on immunosuppression as controls. In group 2(Rejection ; n=15), triple therapy was discontinued to induce acute rejection from postoperative day 5. Plasma concentration of nitric oxide was measured by chemiluminescence method prior to surgery and at postoperative day 9. At postoperative day 9, dogs were sacrificed and rejection was graded pathologically by a working formulation for the standardization of nomenclature in the diagnosis of heart and lung rejection: lung rejection study group.

Plasma nitric oxide level of day 9 was compared to that of prior to surgery in each group. Correlation between plasma nitric oxide level and pathological grade of acute rejection at day 9 in group 2(Rejection) was examined.

In group 2(Rejection), plasma nitric oxide level fo day 9 was elevated significantly, compared to that of prior to surgery(12.28±2.10 vs 6.46 0.57µM/L ; p<0.05).But plasma nitric oxide level of day 9 didn't significantly correlate with the pathological grades of rejection in group 2(Spearman's coefficient r=-0.2094 ; p>0.05).

Plasma concentration of nitric oxide was elevated during acute rejection, but didn't correlate with the pathological severity of rejection.