Alterations in pulmonary surfactant after rapid arousal from torpor in themarsupial Sminthopsis crassicaudata

Torpor in the dunnart, Sminthopsis crassicaudata, alters surfactant lipid c omposition and surface activity. Here we investigated changes in surfactant composition and surface activity over 1 h after rapid arousal from torpor (15-30 degrees C at 1 degrees C/min). We measured total phospholipid (PL), disaturated PL (DSP), and cholesterol (Chol) content of surfactant lavage a nd surface activity (measured at both 15 and 37 degrees C in the captive bu bble surfactometer). Immediately after arousal, Chol decreased (from 4.1 +/ - 0.05 to 2.8 +/- 0.3 mg/g dry lung) and reached warm-active levels by 60 m in after arousal. The Chol/DSP and Chol/PL ratios both decreased to warm-ac tive levels 5 min after arousal because FL, DSP, and the DSP/PL ratio remai ned elevated over the 60 min after arousal. Minimal surface tension and fil m compressibility at 17 mN/m at 37 degrees C both decreased 5 min after aro usal, correlating with rapid changes in surfactant Chol. Therefore, changes in lipids matched changes in surface activity during the postarousal perio d.