Adaptation of a Fish Liver Cell Line (ZFL) to a Taurine Free Medium  

Rosemary Jagus*, Chieh-Lun Liu, Aaron M. Watson* & Allen R. Place
Institute of Marine and Environmental Technology
University of Maryland Center for Environmental Science
Baltimore, MD 21202
jagus@umces.edu

Although the physiological need for taurine in fish has been clearly demonstrated, little is known about the molecular mechanisms regulating its synthesis. Unlike many carnivorous fish, the omnivorous zebrafish has a complete taurine biosynthetic pathway and is not dependent on taurine in the diet, being able to convert methionine into taurine. An adult zebrafish liver cell line (ZFL) has been adapted to taurine free medium to investigate the regulation of taurine homeostasis. Cell culture media all contain taurine provided either by fetal bovine serum (FBS) and/or as a component of the medium. To monitor the effects of taurine, we have successfully adapted an adult zebrafish liver cell line (ZFL) to serum free medium (UltraMEMTM-ITES) and looked at the effects of taurine supplementation on expression of taurine biosynthetic pathway and transporter genes. Addition of taurine to the taurine-free medium had little effect on expression of the biosynthetic pathway genes, ADO, CDO and CSD. Only the taurine transporter, TauT, responds to re-addition of taurine. This successful adaptation of ZFL cells to taurine-free growth has allowed the first investigation of the effects of taurine on expression of taurine biosynthetic pathway and taurine transporter genes in a defined cell type and has also shown that taurine supplementation can stimulate growth. The adaptation strategy described and the synthetic medium used should be applicable to fish cell lines of any aquaculture species.