Effects of high cholesterol diet (0.5% and 1%) on the activity of anti
oxidant enzymes [superoxide dismutase (SOD), catalase (CAT) and glutat
hione peroxidase (GSH-P-x)] in the aortic tissue of rabbits were inves
tigated in the absence or presence of probucol (0.5 gm/kg daily, orall
y). Five groups of ten rabbits each were studied. Group I, regular rab
bit chow diet; Group II, chow + 0.5% cholesterol; Group III, chow + 0.
5% cholesterol + probucol; Group IV, chow + 1% cholesterol and Group V
, chow + 1% cholesterol + probucol. The aorta was removed at the end o
f 4 months for measurement of the antioxidant enzymes. An increase in
activity of aortic antioxidant enzymes was noted in cholesterol-fed ra
bbits (Groups II and IV), being similar for SOD and catalase but highe
r for GSH-P-x in Group IV as compared to Group II. Probucol was ineffe
ctive in altering this cholesterol-induced increase in enzyme activity
except in Group III where it increased the activity of GSH-P-x. These
results suggest that aortic antioxidant enzymes are affected in hyper
cholesterolemia and that probucol is ineffective in altering the aorti
c antioxidant enzyme activity except GSH-P-x activity which increased
in 0.5% cholesterol-fed The protective effects of probucol against hyp
ercholesterolemic atherosclerosis may be partly due to an increase in
the GSH-P-x activity at low levels of hypercholesterolemia. At higher
levels of hypercholesterolemia, the protective effects of probucol cou
ld be due to its antioxidant activity.