Species variation in lung antioxidant enzyme activities

Exposure of several different animal models to O₂-induced lung injury has revealed marked differences in sensitivity of various species to O₂ damage. These differences may be due in part to variation of cellular antioxidant defenses. To characterize lung antioxidant enzyme activities in different species, we measured lung activities of glutathione peroxidase (GSH-Px), superoxide dismutase (SOD), catalase (CAT), and glutathione S-transferase (GSH S-trans) in rat, hamster, baboon, and human lung. Soluble lung fractions were also fractionated on Sephadex G-150-S columns and GSH-Px activity was measured using both cumene hydroperoxide and H₂O₂. This was done to evaluate non-Se-dependent GSH-Px activity in these lung samples. Human lung was obtained at surgery from patients undergoing lobectomy or pneumonectomy for localized lung tumors. SOD activity was similar for all four groups. GSH-Px activity was higher in rat lung than baboon or hamster lung. Lung CAT activity was variable with the highest activity present in the baboon which revealed a lung CAt activity 10 times higher than activity present in the rat. Lung GSH S-trans activities were higher in hamster, baboon, and human lung than in rat lung. Non-SE-dependent GSH-Px was present in rat lung but absent in hamster, baboon, and human lung. We conclude that the hamster was the best model of the animals studied for mimicking human lung antioxidant enzyme activities. Rat lung antioxidant enzyme activities were markedly different from any of the other species examined.