Published online by Cambridge University Press: 16 July 2012
European Community regulations on chemicals promote alternative methods to testsubstances presenting potential risks for the environment. In the present work, culturedatrial cells isolated from oyster (Crassostrea gigas) were used as anexperimental model to investigate the toxicity of tributyltin (TBT) aftershort-time exposure at concentrations representative of those that can be measured inseawater, marine sediments and/or bivalves bioaccumulating this pollutant. Invitro and in vivo assays produce values of the same order ofmagnitude for both animal/cell survival and heart/cardiomyocyte beating rate. The survivalrate of whole animals decreased from 10-6 M TBT after 3 days.For cultured cells, the viability, evaluated using 3-(4, 5-dimethylthiazolyl-2)-2,5-diphenyltetrazolium bromide (MTT) assay, significantly decreased after two days oftreatment with 10-6 M TBT, and after six days with10-10 M TBT. The percentage of apoptotic cells, quantifiedby flow cytometry and YO-PRO®-1 iodide, a nucleic acid stain that onlypermeates cells that are beginning to undergo apoptosis, increased significantly in thesecases. Moreover, intracellular concentration of Ca++ had increased after 10 minof exposition to 10-6 M, and could be associated with apoptotic processes. Aspatch clamp experiments showed that Ca++ conductance was decreased,intracellular calcium increase could mainly be due to a release from internal stores. Thedecreases in beating rhythm could be explained by the decrease in adenosine triphosphate(ATP) production revealed by 31 P nuclear magnetic resonance (NMR) spectroscopyand confirmed by the increase of the KATP channel conductance. The relatedhyperpolarization and the disturbances of the energetic metabolism were clearly related tothe loss of the atrial cell contractility and viability.