Transalveolar fluid absorption ability in rat lungs preserved with Euro- Collins solution and EP4 solution

Background. Pulmonary reimplantation response, presenting lung edema, is a major obstacle of lung transplantation. Transalveolar fluid absorption mechanism, regulated by active transalveolar Na⁺ transport via Na⁺ channel and Na⁺-K⁺-ATPase, is considered to be essential for resolution of lung edema. We investigated the effect of lung preservation on this fluid transport mechanism. Methods. The rat lungs were flushed and preserved with either EP4 solution (EP4) or Euro-Collins solution (EC). First, we determined the basal transalveolar fluid movement by calculating alveolar fluid clearance (AFC) after pulmonary flushing, 24- and 72-hr preservation. Then, we assessed the effects of Na⁺ channel blocker, amiloride, and Na⁺-K⁺- ATPase inhibitor, ouabain, on AFC after 24-hr preservation. We further measured lung ATP content and Na⁺-K⁺-ATPase activity after 24-hr preservation to evaluate cellular metabolism and enzymatic activity during preservation. Results. We found that the lungs preserved with EC showed significantly lower AFC and less inhibitory effects of both blockers than with EP4 after 24-hr preservation. Na⁺-K⁺-ATPase activity was significantly lower with EC than with EP4, even though lung ATP content was not affected by preservation solution. Conclusions. EP4 preservation provides a better environment for maintaining transalveolar fluid absorption mechanism than EC preservation. Therefore, lung preservation with EP4 may ensure more reliable ability in resolving pulmonary edema.