Effects of tributyltin chloride in ascidian embryos: modulation of kinase-mediated signalling pathways

Abstract

We studied the effects of various TBT concentrations by assaying the activity of ERK 1/2 (p44/42)
and phospho-ERK1/2 (phospho-p44/42), proteins with a key role in ascidian development, and
tyrosine kinase-dependent pathway. The effects of this xenobiotic and the role of some signalling
mechanisms on ascidian embryos were examined by using Western immunoblotting. The tyrosine
phosphorylation pattern in the ascidians Ciona intestinalis and Phallusia mammillata development was examined and different levels of protein phosphorylation were found as a response to TBT at µM
range. To determine whether another key signalling pathway was activated, the effects of TBT on the
phosphorylation state of a component of tyrosine kinase-mediated signal transduction MAPK, ERK 1/2
(p44/42) were evaluated. Embryos of Ciona intestinalis exposed to 0.1, 0.25 and 0.5 µM TBT showed
a slight decrement in the level of phosphorylated ERK, while a remarkable decrement in level of
phopshorylated ERK were observed at higher TBT concentrations (0.5 µM to 10 µM). These data
indicated that exposures to TBT induced changes in the total pattern of phosphotyrosine and in the
phosphorylation levels of ERK 1/2 but there were no changes on the overall level of total ERK in
ascidian embryos.