title: Appearance of dark keratinocytes following intracutaneous injection of cholera toxin in mouse skin.
abstract: Intracutaneous injection of cholera toxin (CT), exotoxin of Vibrio cholerae, induces epidermal hyperplasia in mice, rats, and hamsters. In the work reported here we found that, like other hyperplasiogenic compounds such as 12-O-tetradecanoylphorbol-13-acetate which are tumor promoters, CT induces dark basal keratinocytes (dark cells) in the epidermis of mice. These are distinct from other epidermal cells since they contain dense cytoplasm rich in ribosomes and tonofilaments. This was demonstrated by electron microscopy and by toluidine blue staining of paraffin- or Epon-embedded sections. They comprised 3.1% of interfollicular basal cells 24-64 h after injection of 1 ng CT as compared with 0.5% in saline-injected skin. It was found by autoradiography of paraffin sections that about 47.2% of dark cells were labeled with [3H]thymidine at these times, while under the same conditions, labeling indices of basal cells were about 30% at the peaks. These results are discussed in relation to tumor promotion in two-stage carcinogenesis of mouse skin.
mesh_terms: D000818:Animals; D002455:Cell Division / Q000187:drug effects; D002772:Cholera Toxin / Q000008:administration & dosage / Q000494:pharmacology*; D004247:DNA / Q000096:biosynthesis; D004817:Epidermis / Q000187:drug effects* / Q000648:ultrastructure; D007271:Injections, Intradermal; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D008854:Microscopy, Electron
chemical_list: D004247:DNA; D002772:Cholera Toxin