Biochemical characteristics of lungs in senescence-accelerated mouse (SAM).

This study examined age-related biochemical changes of the lung in an animal model of senile lung, senescence-accelerated mouse (SAM). Bronchoalveolar lavage (BAL) was performed on two strains of SAM, the senescence-prone strain (SAM P2) and the senescence-resistant strain (SAM R1), as well as on normal ageing C57 black mice (C57BL), aged 1-24 months. Elastase-like and elastase inhibitory activity of BAL fluid (BALF), glutathione (GSH) and oxidized GSH (GSSG) content both of BALF and lung tissue, and oxygen radical generation of free lung cells obtained by BAL were examined in the three strains of mice. Cell populations did not change throughout the life in SAM strains and C57BL. The elastolytic activity in SAM was greater than in C57BL, but there was no change with age. Both a decreased content of GSH and an increased oxidation of the GSH in BALF were markedly observed with ageing in SAM P2. In the lung tissue, the GSSG/GSH ratio in SAM strains was consistently greater than that in C57BL, suggesting that the GSH redox cycle of the lung may be impaired in SAM strains. The oxygen radical generation by free lung cells increased with age in all three strains, but the increase was earlier and more pronounced in SAM P2 than in the other two strains. In conclusion, an impaired GSH redox cycle and an increased formation of oxygen radicals are observed in the lungs of SAM with increasing age.