Elliott, G., C. Pool, and P. Bruijnzeel. Isolated pig ears: An in vitro model for screening for irritant chemicals using stimulation of transepidermal water loss as the test parameter.

ATLA 1999. 27: 110.

The purpose of this study was to evaluate the effect of some standard chemicals on the transepidermal water loss (TEWL) of pig ear skin as a model for screening for irritants. The chemicals used were those chosen by ECVAM in their challenge issued in March 1998, i.e. decanol, 2-propanol, octanoic acid, decanoic acid, lauric acid, methyl caproate, methyl laurate, methyl palmitate, isopropyl palmitate, sodium dodecyl sulfate and 20% dimethyldodecyl aminobetaine. Ears from domestic white pigs (obtained from an abattoir) were cleaned and shaved. Exposure sites (± 2 cm diameter, free of damage, scratches, grazes, etc.) were marked using a permanent marker. Ears were then placed in a controlled environment (± 30 C, 30-40% humidity) for 30 minutes, after which the control TEWL (g water/m3/hour) was measured (Evaporimeter probe 2105, ServoMedÒ, Stockholm, Sweden). Chemicals were applied using cotton buds (200 ul/chemical). Waxes were melted at 37 C before application. After 4 hours, the test areas were washed with warm water and the ears were dried. After equilibration for 30 minutes, the new TEWL was measured. The absolute alteration in TEWL over the 4-hour exposure period was used as a measure of irritancy. When a cut-off point of 6 g water/m3/hour was used, we were able to accurately predict the classification, non-classified (NC), or irritant (R38), in eight of the chemicals tested. The test system underclassified the amphoteric compound dimethyldodecyl aminobetaine (R38 in human and rabbit studies) and possibly, the wax decanoic acid (R38/NC in humans and R38 in the rabbit).