Application of an In Situ Hepatic and Gill CYP1A Activity Assay to River Water Quality Monitoring Using the See-through Medaka, Oryzias latipes

To monitor monthly water quality in two Japanese rivers, we measured in situ hepatic and gill CYP1A activity in living see-through medaka by a method we had developed previously. The Sakura River is seasonally polluted by pesticides, and the Sakai River receives treated wastewaters from a waste disposal landfill site. Following exposure of the medaka for 24 h to water samples we determined hepatic and gill CYP1A activity by fluorescence microscopy. Exposure to river waters from both sites induced CYP1A activity in the liver and gills. This study confirms the practical usefulness of this method for monitoring environmental water quality.