74.4 Friday, Jan. 6 Effects of lipid-lipid and lipid-water interactions on cutaneous water loss in the house sparrow (Passer domesticus) across temperature and humidity regimes CHAMPAGNE, AM*; ALLEN, HC; WILLIAMS, JB; The Ohio State University; The Ohio State University; The Ohio State University email@example.com
Cutaneous water loss (CWL) accounts for over half of total water loss in birds. The barrier to water loss through the skin is the stratum corneum (SC), the outermost layer of the epidermis. The SC is composed of corneocytes embedded in a lipid matrix of cholesterol esters, fatty acid methyl esters, triacylglycerides, free fatty acids, cholesterol, ceramides, and cerebrosides. The relative abundance of these lipid classes may affect the barrier properties of the lipid matrix by affecting the ability of the lipid molecules to pack together or interact with water molecules to prevent CWL. In this study, we acclimated House Sparrows (Passer domesticus) to different temperature and humidity regimes and measured their CWL at different ambient temperatures. We then used infrared (IR) spectroscopy to measure lipid-lipid and lipid-water interactions in extracted SC of these birds at different temperature and hydration levels. We found that as temperature increases, CWL increases and lipid chains become more disordered. These results suggest that a subset of lipids undergo a phase change from a solid to a liquid phase, which increases SC permeability. In addition, as the SC is hydrated, lipid chain order does not change, and water molecules take on an ordered structure. These results indicate that polar lipid headgroups may order water to slow its permeation through the lipid matrix.