Effects of paraquat on Mg(2+)-ATPase activity in rat liver.
Intraperitoneal injection of paraquat (70 mg/kg) elicited a significant decrease of 20% in activity of Mg(2+)-ATPase in hepatic mitochondria, which is always surrounded by a high concentration of oxygen, in rats. The decrease of mitochondrial Mg(2+)-ATPase activity was completely abolished by pretreatment with vitamin E, which is a scavenger of oxygen radicals. On the other hand, paraquat administration did not change the Mg(2+)-ATPase activity in endoplasmic reticulum, which exists in an anaerobic condition in living cells. When liver microsomes were incubated with 1 mM paraquat under aerobic conditions, the Mg(2+)-ATPase activity was decreased by 42%. The decrease of Mg(2+)-ATPase activity was completely eliminated by pretreatment with vitamin E. Furthermore, lipid peroxidation in microsomes was tremendously increased by the addition of 1 mM paraquat under aerobic conditions. The increase of lipid peroxidation was completely abolished by preadministration of vitamin E in rats. The results suggest that the inhibition of Mg(2+)-ATPase activity induced by paraquat may be mediated by active oxygen, which is produced by the reaction of paraquat radicals; molecular oxygen may be involved in the induction of hepatic cell injury.
Noguchi
N
N
Department of Environmental Medicine, University of Tsukuba, Ibaraki, Japan.
Yamamoto
H
H
Misawa
S
S
D000818:Animals; D017301:Ca(2+) Mg(2+)-ATPase / Q000037:antagonists & inhibitors*; D015227:Lipid Peroxidation / Q000187:drug effects; D008297:Male; D008862:Microsomes, Liver / Q000187:drug effects* / Q000201:enzymology; D008930:Mitochondria, Liver / Q000187:drug effects* / Q000201:enzymology; D010269:Paraquat / Q000633:toxicity*; D051381:Rats; D017207:Rats, Sprague-Dawley
D017301:Ca(2+) Mg(2+)-ATPase; D010269:Paraquat