A cell proliferation assay for small fish and aquatic invertebrates using bath exposure to bromodeoxyuridine

Abstract

A method is described for bath-labeling small fish, bivalves and crustacea with thymidine analogs to quantify cell proliferation. Medaka ( Oryzias latipes), clams ( Mya arenaria) and copepods ( Pseudodiaptomus coronatus) were exposed to waterborne bromodeoxyuridine (BrdU, 30 mg/l) and fluorodeoxyuridine (FdU, 3 mg/l). A simple spectrophotometric method was developed to monitor uridine uptake from the water by animals. BrdU incorporation into nuclei was detected immunohistochemically, allowing estimation of a proliferation index for different organs and cell types. Bath exposure to BrdU will be useful in study of the response of organisms to chemicals such as epigenetic carcinogens that alter rates of cell proliferation especially in organs with a normally low turnover rate, such as the liver. The procedures may also be applied as an assay for growth, in so far as cell division is central to organism growth.