Abstract
Background: Tributyltin (TBT) has been recognized as an environmental pollutant, particularly in the marine environment, and may impair cellular functions in many organisms, thus being classified as a controlled substance by the European Union. However, the mechanisms underlying TBT cytotoxicity remain largely elusive. The aim of this study was to investigate the effect of TBT on cell growth and metabolic profile using the unicellular yeast Saccharomyces cerevisiae as an experimental organism.
Methods: Cell growth was evaluated under the optical microscope by determining the cell number, viability, budding and morphology following exposure to 5-30µM TBT of asynchronous yeast cultures growing through to post-logarithmic phase at 27oC for 24h. TBT was administered at various time points during the lag (1-3h) and logarithmic (3-22h) phases of growth and at the diauxic shift (22h). The cellular metabolic profile was investigated by measuring the levels of glucose, trehalose and glycogen by the anthrone method for carbohydrate determination at different time points during yeast growth. Each set of experiments was performed 6 times. Statistical analyses were performed by analysis of variance (Anova) and non-parametric tests. Control cultures in the absence of any agent were included in all experiments.
Results: TBT dose-dependently inhibited the growth of fast-growing cells (P<0.5), without affecting the proportion of budding yeast cells (P>0.5). The observed effects were more pronounced when TBT was administered at the lag and logarithmic phases (P<0.5), whereas no significant alterations were observed during the diauxic shift (P>0.5). Moreover, TBT induced dose-related morphological alterations to the yeast cells, characterized by the emergence of large intracellular vacuoles approximately 1h after administration. Interestingly, during the diauxic shift, glycogen and trehalose levels were significantly higher (P<0.5) in TBT-treated cells compared to control cultures.
Conclusions: In conclusion, in accordance with previous observations, our results suggest that TBT affects rapidly growing cells. Moreover, they indicate that carbohydrate metabolism may be implicated in the inhibitory action of TBT in the eukaryotic cell cycle and proliferation.
MK and AM contributed equally
