The Distinct levels of glutathione S-transferase activity in gills and liver of sea lamprey (P. marinus L.) juveniles is apparently related with geographical origin

Abstract

Environmental factors in aquatic habitats can influences physiological functions of Petromyzon marinus L. that determine the success of its trophic migration towards the sea. However, glutathione S-transferases (GST), a multifunctional family of microsomal and cytosolic conjugation enzymes, increases the hydrophilicity of several electrophilic chemicals, generating GSH-conjugates easily eliminable. This response may contribute for a better survival of fish species to exogenous substances. The main purpose of this study was to determine liver and gills GST activities of P. marinus juveniles subjected to NaCl gradient up to 35 PSU, during 30 days in aquaria. Sampling occurred at the beginning of the sea lamprey downstream migration in Lima, Vouga, and Mondego portuguese river basins. Cytosol and microsomes obtained by differential centrifugation of tissues homogenates, were used for enzymes determination. The results show that P. marinus juveniles from the Vouga and Lima basin had the highest values of gills mGST and cGST activities after 30 days in freshwater, but were not affected by salt exposure (p<0.05). In addition, individuals from the Vouga basin kept in freshwater also exhibit the highest values of hepatic cGST activity, but in this case the salt gradient caused a significant decrease of this activity to similar levels of individuals from the Lima basin. The P. marinus juveniles from the Mondego basin exhibited the highest levels of hepatic mGST activity. Also in this case, the salt gradient caused a decrease of this activity to values close to those detected in P. marinus juveniles from Vouga and Lima basin which did not change due to salt exposure (p<0.05). The distinct induction of GST subunits in gills and liver of sea lamprey juveniles, is apparently related with its geographical origin, and in the case of the gills did not change after salt exposure, which might be responsible for differences in the survival of the individuals.