Age-related changes in lung structure and function in the senescence-accelerated mouse (SAM): SAM-P/1 as a new murine model of senile hyperinflation of lung

Age-related changes in lung structure and function were investigated in murine models of accelerated senescence (SAM-P/1) and of normal aging (SAM-R/1). In morphometric studies, most of the parameters examined, including lung volume, mean linear intercept, total alveolar duct air volume, and total alveolar air volume, began to increase and the internal surface area per unit lung volume and total elastic fiber length per unit lung volume began to decrease from 2 months of age, and these changes continued to progress up to 10 months of age in SAM-P/1. In SAM-R/1, there were no significant changes in these parameters from 2 to 6 months of age, thereafter slight but steady changes were observed up to 25 months of age. Thus, significant differences in these parameters between SAM-P/1 and SAM-R/1 became evident in mice 6 to 17 months of age. Internal surface area and total elastic fiber length showed no age-related changes after 2 months of age, and total alveolar air volume showed no age-related changes after 6 months of age in either strain. All morphometric parameters examined showed similar levels at 17 months of age in SAM-P/1 and 25 months of age in SAM-R/1. Histologic observations revealed no evidence of destruction of the alveolar wall or elastic fibers in the lung.