IN-VITRO SKIN PENETRATION CHARACTERISTICS OF ETHANOL IN THE RABBIT, MOUSE, RAT, AND HUMAN

The cutaneous penetration of chemicals can be measured by in vitro tec hniques using a wide variety of animal and human skin samples. In cont rast to dermal penetration studies using whole animals, in vitro techn iques allow the direct measurement of chemical penetration, which can be used to help predict the absorbed dose and rate of absorption in wh ole animals and across species. Thus, in vitro methods may provide res ults that allow better extrapolations of in vivo animal studies to hum an exposure scenarios, and more accurate assessments of the potential human health risk following dermal exposure to chemicals. When conduct ing in vitro skin penetration studies, it is critical to know the cond ition and integrity of skin samples being used. Skin samples that have been improperly handled and/or stored can yield results that either u nderestimate or overestimate true penetration characteristics. To avoi d this, ethanol was used as a model compound to assess the quality of skin samples used for skin penetration studies. During each experiment al session, the penetration characteristics of a 25% aqueous solution of [C-14]ethanol were measured and the results compared with values ob tained from similar control experiments conducted previously. This pap er describes the compilation of ethanol penetration data collected ove r 6 years using full-thickness rat, mouse, rabbit, and human skin samp les from over 175 experiments. In general, the results showed that the order of skin permeability for this model compound was rabbit > mouse > rat congruent to human. More important, however, is that this uniqu e data base has allowed the statistical description of the distributio n of such data and, from this, has established skin penetration criter ia of ethanol as a reference chemical that can be used to assess the c ondition and integrity of skin samples used for in vitro skin penetrat ion studies.