The aim of this study was to investigate the interaction of selected toxic heavy metals with fish ABC transport proteins using PLHC-1 fish cell line as in vitro model. Cells were exposed for 24 h to 0.3–3 μM of CdCl 2 , HgCl 2 , As 2 O 3 , Sb 2 O 5 or K 2 Cr 2 O 7 , and the expression of a series of ABC genes was then determined by qRT-PCR: abcc1-5 and abcc10 (encoding for Multidrug Resistance Associated Proteins, MRPs); abcb1 (P-glycoprotein; P-gp) and abcg2 (Breast Cancer Resistance Protein; BCRP). Abcb1, abcc2, abcc3 and abcc4 genes were dose-dependently up-regulated by As 2 O 3 ,K 2 Cr 2 O 7 and HgCl 2 . HgCl 2 was the most effective metal, resulting in the 16-fold increase in expression of abcc2, followed by abcc3 (4-fold vs. control, unexposed cells) and abcc4 (2.5- fold). K 2 Cr 2 O 7 significantly up-regulated abcb1 (5.3-fold), abcc2 (3.4- fold) and abcc3 (2.8-fold), while As 2 O 3 up-regulated abcc2 (3.3-fold). In addition, transport activity of corresponding proteins was evaluated upon exposure to selected metals in the wild type (PLHC-1/wt) and P- gp over expressing doxorubicin resistant cells (PLHC-1/dox), using accumulation assay with monochlorbimane and Calcein-AM as model substrates, respectively. All metals showed a significant inhibition of both P-gp and MRP related transport activities, with IC50 values below 1 μM. In conclusion, our results indicate that (1) specific fish ABC transporters may be actively involved in cellular defense against toxic heavy metals, and (2) some of the tested heavy metals effectively inhibit ABC protein(s) transport activity. doi:10.1016/j.cbpa.2010.06.104 7. Marisa topless: What platinum may bring about H.-R. Köhler, R. Osterauer, L. Marschner, M. McKee, O. Betz (University of Tübingen, Germany); M. Gerberding (Max-Planck-nstitute for Developmental Biology, Tübingen, Germany); B. Sawasdee (Univer- sity of Tübingen, Germany); P. Cloetens (European Synchrotron Radiation Facility Grenoble, France); N. Haus, B. Sures (University of Duisburg-ssen, Germany); R. Triebskorn (University of Tübingen, Germany; Transfer Center for Ecotoxicology and Ecophysiology, Rottenburg, Germany) An external calcareous shell characterizes the archetypal body plan of conchiferan molluscs. Nevertheless, shell internalization into the body has evolved independently in a number of taxa, including some gastropods. In this class, the developmental process of torsion, a process in gastropod ontogenesis that rotates the visceral body 180° relative to the larval headfoot region in counter-clockwise direction is regarded as a hallmark associated with a new anatomical configuration which is present in extant non-heterobranch gastropod species (formerly known as ‘prosobranchs’), predominantly bearing external shells. Short-term platinum exposure uncouples at least two of the processes associated with torsion during the embryonic development of the freshwater snail Marisa cornuarietis (Ampullariidae). Even though the anus of the Pt-treated snails is located anteriorly (which corresponds to the archetype), the gill and the designated mantle tissue remains in a posterior location and thus prevents the formation of an external shell. Similar to the situation in the belemnites, a phragmocone-like internal shell which persists across the lifetime is induced even after pulse treatment with Pt for just one to two days during embryogenesis. We observed the effect of induced snail-slug conversion also in the pulmonate Planorbarius corneus. Although we do not claim to artificially repeat exactly what has evolved in squids and slugs our findings demonstrate that selective alteration of embryonic key processes can result in fundamental body plan changes. doi:10.1016/j.cbpa.2010.06.105 POSTER PRESENTATIONS 8. Cadmium affects nematocytes discharge and cell volume regulation A. Marino, R. Morabito, G. La Spada (University of Messina, Italy) Cnidarians viability depends on some physiological features such as discharge capability and cell volume regulation. Discharge is an exocytosis process consisting in the rapid eversion of the tubule and release of toxins stored in the nematocyte, the highly specialized cell typical of Cnidarians. Both mechanoreceptors and chemoreceptors are needed to perform this peculiar response. With regard to cell volume regulation, essential for cell survival, isolated nematocytes can regulate their volume in hyposmotic conditions (Regulatory Volume Decrease, RVD) activating different channels and cotran- sporters. Therefore we aimed to verify the effect of Cadmium, a toxicant accumulated in the environment due to industrial activities, on Cnidarians viability by investigating nematocytes discharge and cell volume regulation. Experiments were performed on acontia (mesenterial filaments bearing nematocytes) of Calliactis parasitica (Anthozoa) collected in the Strait of Messina (Italy). Discharge tests have been set up by a non-vibrating test probe on tissue, with or without Cadmium, to verify discharge response under both mechan- ical and chemical stimulations. The number of discharged nemato- cytes was then counted. Cell volume regulation was studied on nematocytes isolated from acontia by 605 mM SCN—plus 0.01 mM Ca 2+ application and submitted to 35% hyposmotic shock with Cadmium. Results showed a significant impairment of discharge response under chemico-physical stimulation and an inhibition of RVD capability. Taken together these preliminary findings show that the survival of the entire animal may be affected by exposure to Cadmium and suggest Cnidarians as indicators of water quality. doi:10.1016/j.cbpa.2010.06.106 9. Cadmium impairs RVD in the digestive cells of Mytilus galloprovincialis C. Faggio, A. Torre, D. Alberghina, G. Piccione, F. Trischitta (Università di Messina, Italy) It is known that most cells are able to regulate their volume in anisotonic conditions. When exposed to hyposmotic medium they rapidly swell and thereafter exhibit a regulatory volume decrease (RVD), due to a net loss of intracellular solutes followed by an obliged water efflux. In this work we evaluated if the hepatopancreas cells of Mytilus galloprovincialis are able to perform RVD under hypotonic shock and if heavy metal pollution can affect this homeostatic response. The ability to perform RVD was evaluated by videometric technique in isolated cells both in the absence and in the presence of cadmium, one of the major metal contaminants in the aquatic environment. We found that 56% of cells exposed to hypotonic solution (π from 1100 mOsm to 750 mOsm) were able to regulate cell volume, while 44% of cells rapidly swell by about 15% of their original volume and maintained the value attained throughout the observation period in hypotonic conditions. However in the presence of inhibitors of various transport pathways, known to be involved in RVD, cell volume showed a significantly larger increase. These results suggest that most digestive cells have the ability to perform RVD while a smaller number have a partial capacity to perform RVD, avoiding a large increase in cell volume. Preincubation with CdCl 2 (1 μM) for 30, S37 Abstracts / Comparative Biochemistry and Physiology, Part A 157 (2010) S35–S39