UC Riverside

The pulmonary surfactant system is a multifaceted and highly complex mixture of lipids and proteins that work to reduce the surface tension created at the air-liquid interface within the lung, and provide innate immunity to the lung. Reducing surface tension allows for lung stability, patency and functioning, a crucial task to undertake in oxygen-limiting environments, such as high altitude. The lower partial pressures of oxygen and colder ambient temperatures found at high altitude pose a functional and metabolic challenge to the lung and possibly lung surfactant as well. Therefore, we determined the effects of high altitude hypoxia on the lipids and proteins of the lung surfactant system in adult deer mice. Because deer mice are known to exhibit physiological and genetic adaptations to high altitude, we hypothesized that mice would up-regulate the amounts of lipids and proteins in order to maintain lung stability and function. Specifically, the amounts of saturated lipids will increase to aid in decreasing surface tension, thereby preventing alveolar collapse, and the proteins will have a correlated response given that lipids and proteins work in unison to lower surface tension. Furthermore, since the cholesterol component of lung surfactant is known to increase the fluidity of surfactant layer, thereby promoting proper function, we determined the changes in cholesterol amounts under hypoxia and cold temperatures. These questions were addressed by simple acclimation of mice to low (380 m) and high (3800 m) altitudes and cold (5°C) or warm (25°C) temperatures. Lung surfactant was obtained via lung lavage, lipids or proteins analyzed, blood samples taken and organs dissected.