Objective: To investigate the protective effect of morphine hypoxic preconditioning on hepatic hypoxic/reoxygenation injury in rabbits and the mechanisms involved.
Methods: Hypoxic/reoxygenation injury was induced with inhalation of 8% O2 for 3 hours followed by air for 3 hours. Thirty male white New Zealand rabbits were randomly divided into 3 groups: normal control group (N group), hypoxic/reoxgenation group (H/R group) and morphine hypoxic preconditioning group (MO + H/R group). Animals in the H/R and MO + H/R groups received 5 mL of saline or 3 mg/kg of morphine respectively before the induction of hypoxic injury. Hepatic apoptosis was determined quantitatively by terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) methods. The activity of superoxide dismulase (SOD) in liver tissues was measured at the end of reoxgygenation.
Results: A large number of TUNEL positive cells [(9.50 +/- 1.00)%] were observed in hepatic tissues of rabbits in the H/R group. The administration of morphine exerted a significant anti-apoptotic effect, as evidenced by reduced TUNEL-positive staining [(2.20 +/- 0.40)%, P < 0.05 vs. H/R group]. Compared with the H/R group, treatment with morphine increased SOD activity significantly [(85.57 +/- 19.37) vs. (48.35 +/- 15.84), P < 0.05)].
Conclusion: Morphine hypoxic preconditioning can protect rabbits against acute hepatic hypoxic/ reoxygenation injury by increasing SOD activity and reducing hepatic apoptosis.