1. Oxygen free radicals have been suggested to be a contributory facto
r in complications of diabetes mellitus. In the present study, we inve
stigated the lipid peroxide level [thiobarbituric acid-reactive substa
nces (TBARS)] and activities of antioxidant enzymes (superoxide dismut
ase, catalase and glutathione peroxidase) in aorta, heart and blood of
control and streptozotocin-induced diabetic rats at various stages of
development of diabetes (0 to 6 weeks). 2. There was no change in the
TBARS levels of aorta, heart and blood in the control group, A signif
icant (P<0.05) increase in TBARS levels of aorta, heart and blood was
observed in the diabetic group. 3. There were no significant changes i
n the activities of superoxide dismutase, catalase and glutathione per
oxidase in the aorta, heart and blood of control rats at all time inte
rvals. In the diabetic group, there was a significant (P<0.05) increas
e in the activity of superoxide dismutase and glutathione peroxidase i
n aorta from the fourth week onwards while the activity of catalase in
creased at all time intervals, In the heart of diabetic rats, the acti
vity of total superoxide dismutase and Cu-Zn-superoxide dismutase incr
eased significantly (P<0.05) from the second week onwards while activi
ty of Mn-superoxide dismutase decreased at the fourth week and increas
ed at the sixth week. The activity of catalase and glutathione peroxid
ase increased significantly (P<0.05) at all time intervals. In the blo
od, the activity of superoxide dismutase and glutathione peroxidase in
creased from the third week while catalase activity increased from the
fourth week. 4. The present findings suggest that oxidative stress st
arts at early onset of diabetes mellitus and increases progressively.