EVALUATION OF MICROSOMAL AND CYTOSOLIC BIOMARKERS IN A 7-DAY LARVAL TROUT SEDIMENT TOXICITY TEST

Rainbow trout (Oncorhynchus mykiss) sac fry (larvae) were exposed to R iver Po sediments for 7 days. The sediments were collected in the Rive r Po at two sites located upstream and downstream of the confluence of a polluted tributary, the River Lambro. An additional sediment treatm ent was also tested, in which trout larvae were kept from direct conta ct with the downstream sediment by interposing a Teflon net. Benzo[a]p yrene hydroxylase (AHH), ethoxyresorufin-O-deethylase (EROD), aminopyr ine-N-demethylase (APDM) and UDP glucuronyl transferase (UDPGT) activi ties were found to be significantly induced in whole-body microsomal p reparations of sac fry exposed to the downstream sediment. No signific ant modification was evident in any of the tested cytosolic biomarkers , i.e. glutathione reductase (GR) and glutathione peroxidase (GPx), gl ucose 6-phosphate dehydrogenase (G6PD), 6-phosphogluconate dehydrogena se (6PGD) and the content of nonprotein thiols (SH). With the exceptio n of a slight induction of AHH enzyme activity, no difference could be found between fry exposed to control sediment and those screened from the downstream sediment, suggesting that direct contact with sediment was the major route of exposure to contaminants. This study demonstra tes that several enzyme activities, which are known to occur in juveni le and adult rainbow trout, are also detectable at the sac-fry (larval ) stage, and some of these activities can be induced by a short-term e xposure to a contaminated sediment.