Accumulation of collagen in experimental dermal fibrosis isprevented by propylthiouracil administration. Dermalthickness was determined by using photomicrographs of Masson-stainedsections, by measuring the distance between the epidermal-dermaljunction and the dermal-fat junction at 10 randomly selectedsites/high-power field (HPF), for 10 HPFs per section. Skin fibrosiswas induced in mice by subcutaneous injection of HOCl. The resultantincrease in dermal thickness was significantly reduced bysubcutaneous injection of propylthiouracil. Representative Massontrichrome-stained sections were examined with light microscopy:(A) Normal histology of a representative skin tissueobtained from a Sham mouse; (B) Representative histology ofskin tissue of HOCl mice; (C) Representative histology ofskin tissue of HOCl + PTU mouse (original magnification,×10.);(D) Dermal thickness in mice from the three experimentalgroups (Sham group, n = 5; HOCl group, n = 10;HOCl + PTU group, n = 10). Values are expressed as the meanand SD. *P < 0.001 versus Sham #P < 0.001versus HOCl.