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Cortisol is the main corticosteroid secreted by the interrenal cells of the head kidney and it exerts a role in mantaining the omeostatic status in fish. In teleosts its effects are mediated through intracellular receptors expressed in several tissues, that are ligand-dependent transcription factors by binding to specific tissue DNA sequences. In Dicentrarchus labrax we previously cloned and sequenced a glucocorticoid receptor, DlGR1, isolated from leukocytes of peritoneal cavity. In this work we showed mRNA expression and tissue immunohistochemical localization of brain DlGR1 by in situ hybridization assays, with a riboprobe with DlGR1 cDNA trascriptional activation domain, and by immunohistochemical methods, using a specific antibody for a selected sequence of the receptor tran- scriptional domain. The mRNA and the protein are expressed in pyramidal cells of the optic lobe and in the small globular neurons of the diencephalon.

Blood cells freshly collected from sea bass (Dicentrarchus labrax) were exposed in vitro to different concentrations of cadmium (Cd) and copper (Cu) at 10-7 M, 10-5 M, 10-3 M, and exam- ined for neutral red retention capacity and for cell vitality with MTT assay. A relationship between heavy metal exposure and alteration in responses of blood cells in a dose-time-dependent was found. Our results showed that fish blood cells may constitute an interesting biological model for experimen- tal and applied toxicology, especially in the case of environmental pollution.

Marine environments are continuously being threatened by a large number of xenobi- otics from anthropogenic sources. The effect of chemical pollution on living organisms are numerous and may impair reproductive success of adults species of marine invertebrate and vertebrate through effects on gamete quality. Echinoderms are characterized by external fertilizzation and gametes, free of any type of protection, may be in contact with toxic substances so the reproductive success depends largely on the environment conditions. The purpose of this work is to assess the effects on the in vitro fertiliza- tion of exposure of sea urchin Paracentrotus lividus gametes to xenobiotic substances as CuSO4, CdCl2 and TBTCl. The effect of contaminant were assessed by two experimental set in which gametes were treated with different concentration (0, 10-3, 10-5 10-7 10-9 M) of different substances as CdCl2, CuSO4 and TBTCl. The effects were evaluated as percentage of fertilization. The results showed that the gametes exposure to xenobiotic decreased the percentage of fertilization and that more sensitive to treatment were the sperm cells, propably because the toxic effect affected the motility of the sperm. In conclusion, the absence of fertilization (spermiotoxicity) may submit the toxic effects of these substances to the level of body and may candidate the sea urchis as biosensors for the evaluation of environmental quality.