Immunohistochemical detection of proliferating cell nuclear antigen (PCNA) in tissues of aquatic animals utilized in toxicity bioassays

Cell proliferation is an important component of toxic and carcinogenic mechanisms. A recently developed immunohistochemical assay for proliferating cell nuclear antigen (PCNA) identifies an endogenous marker for cell proliferation in routinely-fixed and paraffin-embedded specimens. This assay was adapted to identify proliferating cells in tissues of several fish species used in toxicity bioassays: medaka (Oryzias latipes), guppy (Poeata), and western mosquitofish (Gambusia affinis). The present studies show that this PCNA technique can identify proliferating cells in aquatic animals if attention is given to primary fixative, primary antibody, protein blocking reagent and antigen retrieval processing. PCNA immunoreactivity was demonstrated in tissues with normally high cell turnover such as gill, gastrointestinal tract and testis. Proliferation was also demonstrated in carcinogen-induced hepatic neoplasms.