Animal models of percutaneous penetration: comparison between Mexican hairless dogs and man

In an attempt to find better animal models for percutaneous penetration studies relevant to man, urinary excretion of 14C-labeled compounds was studied in the Mexican hairless dog and in man. With benzoic acid, progesterone and testosterone, the total absorption and maximum absorption rate were greater in man than in the hairless dog. As urinary excretion lasted days longer in the dog than in man, it is possible that the thin dog skin held the chemicals longer than man. Surface-counting experiments with a Geiger counter with a thin mica window protected by a special screen of fine stainless steel wires showed that benzoic acid and progesterone did persist on the dog skin far longer than on human skin. We conclude that the Mexican hairless dog has permeability characteristics significantly different from those of human skin.