Eydsis or molting of the outer skin is a normal process that occurs several times a year in healthy snakes. The resulting shed snake skin is a sample of pure stratum corneum that is known to behave in a similar fashion to that of human skin. Our overall objective is to create a novel bioassay which utilizes shed snake skin as a natural substrate for toxicological tests. This model should allow one to evaluate changes in the skin barrier when it is exposed to certain environmental agents. These would include corrosives, detergents and solvents which are known to disrupt stratum corneum barrier function. To test the feasibility of this approach, shedding from different types of snakes will be exposed to various chemical insults under varying conditions of dose, time and temperature. Computerized evapotimetry will be used to measure the degree of damage since elevated TEWL rates are typically associated with disrupted barrier function. The test agents will be reference chemicals whose actions on humans are well known. We feel that by combining this instrumental approach with an ex vivo model that is based on a pure sample of stratum corneum, we will open a whole new line of investigations into this aspect of dermal toxicity. These studies should provide faster and cheaper assays not only for detergents but other types of environmental insults that adversely affect the stratum corneum as well. Alternatively, agents that are known to improve skin condition such as moisturizers could also be evaluated. This approach would be ideal for screening formulations before running them in studies employing human volunteers which tend to be very time consuming and expensive. It is especially appealing since the donor animal is not harmed in anyway. Moreover, since a number of candidates will be surveyed to find the most suitable donor species, we may gain new insights into as to how differences in lipid composition and various structural arrangements influence cutaneous water loss rates and if these are related to habitat and/or taxonomic group
