Modulation of xenobiotic metabolism and plasmatic responses by temperature acclimation in juveniles of Solea senegalensis under laboratory conditions

Abstract

Solea senegalensis juveniles (n=48) were acclimatized to two different temperatures, 15ºC and 20ºC, for a period up to 60 days. Several hepatic, kidney, gill, muscular and plasmatic biomarkers were measured over time at the two temperatures. The lower temperature triggered over time the synthesis of hepatic microsomal cytochrome P450 related enzymes (CYPs), using several fluorometric substrates (e.g. EROD), carboxylesterases (CbEs), the conjugating enzyme UDPGT and EROD in gills. Antioxidant enzyme activities in liver did not show a clear pattern in relation to temperature. Basal enzymatic activities after 60 days acclimatization were also elevated for other deethylase activities: MROD, BROD, PROD, CECOD and ECOD. Metallothionein (MT) levels measured in kidney and liver were only responsive to temperature in the liver, but within a narrow range of variation (1.2-­‐1.6 mg/g w.w). Plasmatic markers (osmolality, glucose, lactate and triglycerides) were examined. Osmolality was dependent on temperature and time (T15>T20 and t0>t30>t60) whereas the other parameters were only influenced by the acclimatization time. Glucose and lactate levels were lower at day 30, while triglycerides were higher at this period. The expression of heat shock proteins (HSP70) in muscle increased over time, at 15ºC. No significant changes were observed between temperature groups. The potential effect of temperature on the reproductive system was checked by analyzing vitellogenin and sex steroids (testosterone, 11-­‐keto testosterone and estradiol) in plasma. At day 60, vitellogenin levels were undetectable and no differences were observed for steroids between groups, suggesting no effect of temperature on gonad maturation. The results evidenced that S. senegalensis use the temperature compensation strategy by increasing enzyme activity at lower temperatures and this was clearer for microsomal enzymes involved in xenobiotic metabolism after 60 days