Glutathione peroxidase and catalase activity in rat respiratory muscles. Effect of growth, maturation and aging

Background: Glutathione peroxidase (GSHPx) and catalase are two important c ellular antioxidant enzymes involved in H2O2 and lipid-peroxide metabolism. Aim: To study the effects of growth, maturation and aging on the activity of these enzymes. Material and methods: GSHPx and catalase specific activit ies were measured in samples of diaphragm and intercostal muscle of male Sp rague-Dawley rats of different ages (21, 50, 70, 180 and 365 days), anesthe tised with chloral hydrate (45 mg/100 g ip). Results: The diaphragm and int ercostal muscles did not differ in GSHPx activity at 21 days. After that, G SHPx activity increased progressively with age, but following a different p attern, in each muscle, suggesting an increase in enzyme substrates with ag e. In one year old animals, GSHPx activity was 5 times higher for the diaph ragm and 3 times higher for the intercostal muscles, when compared with val ues observed at 21 days of age. Catalase activity also increased with age i n the diaphragm but not in the intercostal muscles. Conclusions: GSHPx acti vity increases progressively with age in rat respiratory muscles, wit a tim e course that is specific of each muscle. Catalase activity increases with age only in the diaphragm. These results support the hypothesis that antiox idants in respiratory muscles undergo specific regulatory changes with age.