Meeting Abstract
32.4 Jan. 5 β-Glucocerebrosidase activity in stratum corneum of House Sparrows following acclimation to high or low humidity COX, Robert M*; MUNOZ-GARCIA, Agusti; JURKOWITZ, Marianne; WILLIAMS, Joseph B; Ohio State University; Ohio State University; Ohio State University; Ohio State University cox.541@osu.edu
Skin is an important avenue for water loss, so environmental conditions that necessitate water conservation should favor mechanisms that reduce cutaneous water loss (CWL). Skin resistance to CWL is conferred by a barrier of lipid molecules located in the stratum corneum (SC), the outer layer of the epidermis. In mammals, SC barrier function depends upon the conversion of cerebrosides to ceramides by the enzyme β-glucocerebrosidase (β-GlcCer�ase). Avian SC contains both cerebrosides and ceramides, suggesting that plasticity in CWL may be mediated by changes in β-GlcCer�ase activity and resultant SC lipid composition. We tested this hypothesis by acclimating House Sparrows (Passer domesticus) to either dry or humid conditions and then measuring β-GlcCer�ase activity from SC homogenates. Our results provide the first characterizarion of β-GlcCer�ase activity in any non-mammalian vertebrate. Relative to non-acclimated controls, both dry- and humid-acclimated sparrows had significantly elevated β-GlcCer�ase activity at 21 d post-acclimation. Across individuals, we found negative correlations between β-GlcCer�ase activity and both CWL and SC ceramide content. Although dry- and humid-acclimated sparrows did not differ in β-GlcCer�ase activity, these results are consistent with our findings that both humidity treatments caused a reduction in CWL and similar changes in SC lipid composition. Our results demonstrate physiological plasticity in CWL and provide tentative support for a role of β-GlcCer�ase in mediating this response. However, our results refute the hypothesis that ambient humidity is the primary stimulus for CWL acclimation and indirectly suggest that temperature may have an overriding effect on acclimation.
