Paraquat and menadione exposure of rainbow trout (Oncorhynchus mykiss)--studies of effects on the pentose-phosphate shunt and thiamine levels in liver and kidney.
Possible xenobiotic interactions with thiamine were studied in salmonid fish, by repeatedly injecting two model substances, paraquat and menadione, into juvenile rainbow trout (Oncorhynchus mykiss). These two substances were chosen because of their well-known ability to redox-cycle and cause depletion of NADPH in several biological systems. Depletion of NADPH increases metabolism through the pentose-phosphate shunt and may thereby increase the need for thiamine diphosphate by heightened transketolase activity. A special food was produced with lower thiamine content than commercial food, usually enriched with thiamine, which could mask an effect on the thiamine level. After 9 weeks of exposure, glucose-6-phosphate dehydrogenase, transketolase, glutathione reductase and ethoxyresorufin O-deethylase were analysed in liver and kidney cellular sub-fractions as well as analysis of total thiamine concentrations in liver, kidney and muscle. The results showed that paraquat caused a large increase in hepatic glutathione reductase activity and induced hepatic glucose-6-phosphate dehydrogenase activity, i.e., the rate-limiting enzyme in the oxidative part of the pentose-phosphate shunt. Despite this paraquat exposure did not affect transketolase activity and total thiamine concentration.
Akerman
Gun
G
Laboratory for Aquatic Ecotoxicology, Institute of Applied Environmental Research, Stockholm University, SE-106 91 Stockholm, Sweden. gun.akerman@itm.su.se
Amcoff
Patric
P
Tjärnlund
Ulla
U
Fogelberg
Kajsa
K
Torrissen
Ole
O
Balk
Lennart
L
D000818:Animals; D005260:Female; D005954:Glucosephosphate Dehydrogenase / Q000378:metabolism; D005980:Glutathione Reductase / Q000378:metabolism; D007668:Kidney / Q000187:drug effects* / Q000378:metabolism*; D008099:Liver / Q000187:drug effects* / Q000378:metabolism*; D008297:Male; D009249:NADP / Q000378:metabolism; D017686:Oncorhynchus mykiss; D010084:Oxidation-Reduction; D010269:Paraquat / Q000633:toxicity*; D010427:Pentose Phosphate Pathway / Q000187:drug effects*; D013831:Thiamine / Q000378:metabolism*; D014174:Transketolase / Q000378:metabolism; D024483:Vitamin K 3 / Q000494:pharmacology*; D015262:Xenobiotics / Q000633:toxicity
D015262:Xenobiotics; D009249:NADP; D024483:Vitamin K 3; D005954:Glucosephosphate Dehydrogenase; D005980:Glutathione Reductase; D014174:Transketolase; D010269:Paraquat; D013831:Thiamine