Moderating effects of oregano extract (Origanum vulgare L.) on oxidative stress and toxicity
induced by organophosphate pesticide, diazinon (0.287 mg/l) were investigated for the first time
in rainbow trout, Oncorhynchus mykiss by measuring antioxidant and metabolic enzymes. In
non-diazinon-exposed fish, the hepatic levels of total antioxidant capacity (TAC) and antioxidant
enzymes including superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase
(GPX) elevated in fish supplemented with 6 and 10 g ORG/kg diet compared to control group
(non-ORG-supplemented fish). The supplementation of fish with 14 g ORG/kg diet significantly
decreased the hepatic antioxidant enzymes compared to control. The acetylcholinesterase
(AChE) activity and malondialdehyde (MDA) levels remained unchanged in all groups throughout
the experiment. The serum levels of hepatic metabolic enzymes [(aspartate aminotransferase
(AST), alanine aminotransferase (ALT), and lactate dehydrogenase (LHD)] remained unchanged in
all experimental groups throughout the experiment. In diazinon-exposed groups, the activity of
SOD, GPx, and TAC in liver elevated after exposure to diazinon in fish fed 2, 6, and 10 g ORG/kg
diet. The CAT activity increased only in fish supplemented with 6 and 10 g ORG/kg diet. The levels
of all antioxidant enzymes and TAC significantly decreased in control and fish supplemented
with 14 g ORG/kg diet. The AChE activity significantly declined in control and fish supplemented
with 2 and 14 g ORG/kg diet. After exposure to diazinon, the levels of MDA in liver increased in
control and those fed 2 and 14 g ORG/kg diet. In fish supplemented with 6 and 10 g ORG/kg
diet, the MDA levels showed no significant alternations during the experiment period. The
serum levels of AST, ALT, and alkaline phosphatase (ALP) elevated during exposure to diazinon
in control and fish supplemented with 2 and 14 g ORG/kg diet, while these enzymes showed no
significant changes in fish fed with 6 and
