Protective effects of ischemic preconditioning on the cold-preserved liverare tyrosine kinase dependent

Background. Little data exist regarding the use of ischemic preconditioning before sustained hepatic cold storage. We hypothesized that ischemic preco nditioning protects hepatic grafts via a tyrosine kinase-dependent pathway. Methods. Six porcine livers underwent routine harvest (control). Five other livers underwent 15 min of in situ ischemia followed by 15 min of reflow b efore harvest (ischemic preconditioning). Another five livers were pretreat ed with a tyrosine kinase inhibitor (genistein) before preconditioning. Upo n reperfusion and after 2 hours of cold storage, graft function, graft circ ulatory impairment, and markers of cellular damage were analyzed. Tissue cy toplasmic extracts were analyzed for tyrosine phosphorylation with Western blot. Significance was determined with t tests. Results. Ischemic-preconditioned grafts demonstrated enhanced bile producti on, augmented responses to a bile acid challenge, and elevated O-2 consumpt ion (P<0.05) compared to controls. Also, preconditioned grafts demonstrated improved hepatic tissue blood flow and decreased hepatic vascular resistan ce (P<0.005) compared to controls. Endothelial cell preservation (factor VI II immunostain) was improved in preconditioned graft biopsies compared to c ontrols. With genistein pretreatment, all observed improvements returned to control levels. Analysis of cytoplasmic extracts demonstrated an increase in tyrosine phosphorylation before cold ischemia in preconditioned grafts o nly, but not in control or genistein-pretreated grafts. Conclusions. The data indicate that ischemic preconditioning protects the l iver from sustained cold ischemia and that tyrosine kinases are involved in preconditioning responses.