Although IPC (ischaemic preconditioning) is considered as a protective strategy in HI/R (hepatic ischaemia/reperfusion), the mechanisms for this effect have not been fully elucidated. In the present study we investigate whether PPC (pharmacological preconditioning) by transient activation of A1R (adenosine A1 receptor) protects against long-term HI/R and whether the protective effects of IPC depend on A1R activation and whether both preconditionings affect remote organs. Wistar rats underwent IPC and long-term HI/R. Another set of animals were pharmacologically preconditioned with the A1R-agonist CCPA [2-chloro-N6-cyclopentyladenosine; 0.1 mg/kg of body weight, i.p. (intraperitoneally)] 24 h before HI/R. In other groups, rats received an A1R-antagonist, DPCPX (1,3-dipropyl-8-cyclopentylxanthine; 0.1 mg/kg of body weight, i.p.) 24 h before HI/R. Hepatic damage was evaluated by transaminase [AST (aspartate transaminase), ALT (alanine transaminase)] release; inflammation was assessed by hepatic MPO (myeloperoxidase) and serum TNFα (tumour necrosis factor α) and NO; oxidative stress was estimated by MDA (malondialdehyde) and 4-HDA (4-hydroxyalkenals), SOD (superoxide dismutase) activity, GSH and ADA (adenosine deaminase) as adenosine metabolism. Both preconditionings protected liver and lung against HI/R as indicated by the reduction in transaminases, MPO, MDA+4-HDA, NO, TNFα and ADA activity as compared with HI/R (P<0.05). However, pre-treatment with DPCPX abolished the protective effects of IPC and PPC. Preconditionings induced a significant increase in hepatic MnSOD (manganese SOD) activity and NO generation compared with the sham group, and this activity was abolished by DPCPX pre-treatment. A1R activation induced hepatic delayed preconditioning and blockade of A1R abolished hepatic IPC. IPC, as well as PPC, were able to prevent lung damage. These protective effects are associated with a reduction in oxidative stress, inflammation and endogenous antioxidant preservation.

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