A considerable amount of clinical and experimental evidence exists suggesting the involvement of reactive
oxygen substances (ROS) in the aetiology of
uveitis. The activated phagocytic system of polymorphonuclear leucocytes in
uveitis is involved in the generation of ROS. In addition to their direct
free radical scavenging action,
aprotinin,
melatonin and
vitamin C are known to protect against oedema formation and can preserve plasma membrane fluidity and
free radical production. Histological changes in the retina that occur during
uveitis are not well explained. The purpose of this study was to determine whether
vitamin C,
aprotinin and
melatonin can protect the retina from damage accompanying experimental
uveitis (EU). Thirty adult male guinea pigs were divided into five groups of six animals each. The first group was used as control. The right eyes of groups 2, 3, 4 and 5 received an
intravitreal injection of
bovine serum albumin for induction of experimental
uveitis. At the same time and also on the consecutive third day, groups 3, 4 and 5 received
intraperitoneal injections of
vitamin C (
ascorbic acid, 100 mg kg(-1) body wt),
aprotinin (20,000 kIU kg(-1) body wt) and
melatonin (10 mg kg(-1) body wt), respectively. The animals were killed on the sixth day. The average thickness of the retina and inner plexiform layer for each eye was measured in sagittal section near the optic nerve and expressed in microns. The thickness of the retina and inner plexiform layer in the control group was significantly (p < 0.01) lower than in the group EU as compared with the group EU plus
vitamin C, group EU plus
aprotinin, group EU plus
melatonin (p < 0.05). The thicknesses of the retina and inner plexiform layer in group EU plus
vitamin C, group EU plus
aprotinin and group EU plus
melatonin were significantly (p < 0.01) lower than that in the group EU. The difference in thickness of the retina and inner plexiform layer among the groups 3, 4 and 5 was not significant (p > 0.05). In conclusion, this study demonstrated that oedematous effects of EU on the retina were reduced by the administration of intraperitoneal
vitamin C,
aprotinin and
melatonin, i.e. these
antioxidants had significant protective effects on the retina of guinea pigs against oedematous damage in EU. However, the reductive effect of
vitamin C on EU was greater than that of
aprotinin and
melatonin. The intraperitoneal
vitamin C,
aprotinin and
melatonin supplementations may strengthen the
antioxidant defence system because of decreased ROS, and these agents may play a role in treating
uveitis.