ASSESSMENT OF XANTHINE-OXIDASE IN HUMAN LUNG AND LUNG TRANSPLANTATION

Oxygen free radical generation by xanthine oxidase (XO) is a possible mechanism in the injury following reperfusion of transplanted organs, This study was undertaken to investigate XO in human lung, and to inve stigate whether XO is released into the blood stream during the immedi ate postoperative period after Lung transplantation. XO activity was m easured in healthy human lung tissue, and XO protein and the adenine n ucleotide catabolic products hypoxanthine, xanthine and uric acid were analysed in the plasma samples collected during human heart-lung tran splantation (n=4), double lung transplantation (n=2), and single lung transplantation (n=1), Neutrophil degranulation was assessed by plasma lactoferrin measurements. The results indicated that XO activity (det ection limit 5 pmol . min(-1). mg(-1) protein) and protein (detection limit 5 ng . mg(-1) protein) were undetectable in the lungs of five he althy individuals. Similarly, no XO protein could be found in the plas ma samples from the right ventricle or left atrium during and after th e transplantation in any of the cases, Plasma xanthine and hypoxanthin e concentrations were elevated 2-10 fold immediately after the reperfu sion of the transplant, indicating washout of high-energy phosphate de gradation products from the ischaemic lung, Plasma uric acid decreased rather than increased immediately after the surgery and during the fo llowing 24 h. Lactoferrin was elevated during the surgery. In conclusi on, these results show that XO activity in human lung is low, it is no t released into the blood stream during human heart-lung transplantati on, and it is unlikely to contribute to postoperative complications in these patients.