Alterations of nitric oxide synthase expression and activity during rat lung transplantation

Decreased nitric oxide (NO) production has been reported during lung transp lantation in patients. To study the effects of ischemia and reperfusion on endogenous NO synthase (NOS) expression, both an ex vivo and an in vivo lun g injury model for transplantation were used. Donor rat lungs were flushed with cold low-potassium dextran solution and subjected to either cold (4 de grees C for 12 h) or warm (21 degrees C for 4 h) ischemic preservation foll owed by reperfusion with an ex vivo model. A significant increase in induci ble NOS and a decrease in endothelial NOS mRNA was found after reperfusion. These results were confirmed in a rat single-lung transplant model after w arm preservation. Interestingly, protein contents of both inducible NOS and endothelial NOS increased in the transplanted lung after 2 h of reperfusio n. However, the total activity of NOS in the transplanted lungs remained at very low levels. We conclude that ischemic lung preservation and reperfusi on result in altered NOS gene and protein expression with inhibited NOS act ivity, which may contribute to the injury of lung transplants.