Evaluation of the Hairless Rat as a Model for in Vivo Percutaneous Absorption

The study evaluated the hairless rat as a model for in vivo percutaneous absorption by comparing it to the hairy rat. It found that hairless rat skin was a "leakier" barrier for polar compounds like mannitol, with higher absorption rates than hairy rat skin. Progesterone absorption was about five times greater in hairless rats. The study also noted that skin delipidization significantly reduced the barrier to mannitol absorption, especially in hairy rats. Histological analysis suggested that the hairless rat's skin structures, such as patulous cysts and enlarged sebaceous glands, might enhance polar pathways and provide a lipophilic reservoir, highlighting the role of follicular structures in passive percutaneous absorption.