Analysis of free and protein-bound ceramides by tape stripping of stratum corneum from dogs

The free and protein-bound ceramides of dog stratum corneum (SC) were analyzed by thin-layer chromatography after tape stripping of the abdomen of five dogs. The sphingoid bases were identified by gas-liquid chromatography as sphingosine, phytosphingosine, and 6-hydroxysphingosine. Electrospray ionization-ion trap mass spectrometry was used to characterize the protein-bound ceramides containing sphingosine and omega-hydroxy long-chain fatty acids. Although the molecular species were the same ones in all dogs, wide quantitative variations in the patterns of SC ceramides were observed in different breeds of dogs. The free ceramide concentration changed with the depth of SC, with a higher concentration in the deep layers, whereas the concentration of protein-bound ceramides remained constant. These results show that canine SC is close to that of humans with respect to ceramides.