The Hepatoprotective Effect of Nitric Oxide Modulators and Antioxidants in Hepatic Ischemia/Reperfusion Injury in Albino Rats

Warm ischemia/reperfusion injury (IRI) of the liver is a major determinant of the
outcome of a variety of clinical conditions. During the ischemic phase, tissue injury
occurs due to oxygen deficiency. However, much injury arises with the restitution of
the circulation (reperfusion injury), in which the generation of reactive oxygen
species (ROS) plays a fundamental role. Several studies have emphasized the positive
effect of antioxidants in attenuating IRI in many tissues. The role of nitric oxide and
its action as an oxidant/antioxidant is considered. The aim of the present work was to
investigate the potential of NO in modulating warm IRI of the liver and its possible
interaction with different antioxidants in a trial to minimize that injury.
Seventy two albino rats were used in the present study. Rats were classified into
the following groups (8 rats each): The 1st group of rats was subjected to 30min of
ischemia followed by 60min of reperfusion. The 2nd group was Sham-operated rats
underwent the same surgical procedure without interruption of the blood flow to the
liver and served as controls. 3rd group L-nitro-arginine methyl ester (L-NAME)
treated group, 50mg/k g (Sigma), the 4th, 5th, and 6th groups were the NO-donor, L-Arginine (Sigma) treated groups, in 3 different doses (100, 300, 500mg/k g). The drugs
were administered intravenously 5min before ischemia-induction. The 7th group
allopurinol (Sigma) treated group (50mg/k g), the 8th group desferrioxamine treated
group (desferal) (Sigma) 100mg/k g and the 9th group vitamin C treated group
(Sigma) 100mg/k g. Allopurinol was administered intraperitoneally 10min before the
induction of ischemia, whereas desferal and vitamin C were administered
intravenously 5min before the induction of ischemia. The left lobe of the liver of
albino rats was subjected to 30 min warm ischemia followed by 60 min of
reperfusion. Serum liver enzymes (AST, ALT, and LDH) were determined as a
measure of tissue injury. Plasma nitrite level was assessed as a measure of nitric
oxide production. Hepatic levels of malondialdehyde were quantified to evaluate the
oxidative stress, while those of superoxide dismutase, catalase, and glutathione
served as a determinant of the antioxidant status. Thirty minutes of warm ischemia
followed by reperfusion for 60 min inflicted signs of tissue injury accompanied by
oxidative stress and exhaustion of tissue antioxidants and plasma nitrite level. This
was exacerbated with the nitric oxide block er L-NAME. On the other hand, the nitric
oxide donor (L-arginine) its lowest and intermediate doses (100, 300mg/k g) could
attenuate that injury; while in its highest dose (500mg/k g) accentuated the injury.
Treatment with the xanthine oxidase inhibitor (allopurinol) was accompanied with a
mild protective effect. Treatment with the iron-chelating agent (desferrioxamine) was
accompanied with a substantial protective effect, while the treatment with vitamin C
caused a moderate protection. The results clearly demonstrated that nitric oxide
supply during IRI is up to a certain limit beneficial in ameliorating hepatic IRI, while
its paucity was accompanied with accentuation of the injury. It seems that too high or
too low level of NO is detrimental and aggravates IRI and its fine-tuning is a
prerequisite to protect at least hepatic tissue. Furthermore, the results revealed that
the antioxidant allopurinol did not practically improve the deteriorated livers
subjected to IRI. Also, the results proved that iron-chelator (desferrioxamine)
exhibited a very strong protective effect. The role of vitamin C warrants further
elucidation, as its sole administration could confer protection to the liver against IRI.