75.2 Saturday, Jan. 5 Phenotypic Changes in Lung Function After Acclimation to High Altitude in Deer Mice DIAZ, S; SHIRKEY, NJ; THALER, CD; CARDULLO, RA; HAMMOND, KA*; Univ. of California, Riverside email@example.com
Small mammals living at high altitude face low O2 partial pressures, cold ambient temperatures necessitating an increase in energy expenditure. Deer mice (Peromyscus maniculatus) inhabit a broad altitudinal range (0 to 4000 m) in the US and are used as a model species to demonstrate genetic adaptations in hemoglobin O2 affinity. It appears from recent research, however that the hemoglobin/genetic adaptations are insufficient to explain the highly successful active life history of deer mice. Previously, we have reported that deer mice also display phenotypic changes in organ size (heart, lung, gut, and blood volume) that vary along the altitudinal gradient, are linked to the improved aerobic performance necessary for high levels of activity. We have also reported moderate changes in pulmonary surfactant composition that may lead to changes in surface tension to support aerobic activity in the low O2 availability at high altitude. Here we report results showing that although mice living at high altitude produce the same total amount of surfactant lipid as those living at low altitude, 85% of high altitude individuals (n=13) include lipids that were not detected in low altitude mice (n=11). Conversely, 65% of low altitude individuals have lipid species that were not detected in high altitude individuals. Also while there is a nearly double amount of surfactant protein B (responsible for spreading lipids) in mice at high altitude there is enough variability in the levels of this protein so that this difference is not statistically significant. From these results, we predict that subtle changes in surfactant composition are important at high altitude but they must be accompanied by changes in lung architecture (and lung mass).