Metal concentrations and analysis of metal binding protein fractions from the liver of Tilapia collected from Shing Mun River

We determined metal concentrations in tissues of tilapia ( Tilapia mossambica) collected from Shing Mun River. Two sites (Tai Wai and Fo Tan) were chosen for our investigation, and the metal concentrations were higher in liver than in muscle and gills. Copper and zinc concentrations were found to be higher in the liver and gills of tilapia collected from Tai Wai. Pooled liver samples from Fo Tan were analyzed for metal binding proteins. No significant differences were found in male and female fish. Zinc was found to be associated with the cytosolic fraction, whereas copper and cadmium were more associated with the pellet of 15000 g centrifugation. There are four major peaks from the Superdex-75 profiles of the liver cytosolic fractions coeluted with the metal ions. Zinc was found to be mainly associated with the two higher molecular weight peaks, whereas cadmium is more related to a lower molecular weight peak of around 2kDa. Copper eluted mainly with the presumed MT peak and one higher molecular weight peak.