Estimation of cellular thiols metallothioneins (MT s) sensitivity to continuous pressure of environmentalchemical ‘cocktail’ of xenobiotics needs investigation in correct model experiments. The aim of this studywas to elucidate MTs contribution into bivalve mollusk response to co-exposure to xenobiotics and elevatedtemperature. We treated the mussels Unio tumidus Philipson, 1788 (Unionidae) with drugs diclofenac (Dc,2 nM), nifedipine (Nf, 2 nM) or with organophosphonate herbicide glyphosate (Gl, formulation RoundupMA X, 79 nM) separately at 18°C and in combination at 18°C (DcNfGl) and 25°C (DcNfGl+T) during 14 days.MT s were isolated from digestive gland by size-exclusion chromatography. The concentration of MT s in thetissue was assessed according to metals (Zn, Cu, Cd) in the eluted peak of MTs (MT -Me) and thiols (MT -SH)content. Tissue redox status was assessed using lactate/pyruvate ratio. The assay of cells viability was basedon the lysosomes ability of hemocytes to concentrate the Neutral Red (NR) dye. It was found, that MT -SHcontent in the digestive gland was increased under all exposures. Treatment with Dc increased the level ofMT -Me, whereas treatment with Gl decreased it and increased lactate/pyruvate ratio. Nf decreased this ratioby elevating pyruvate level and increased lysosomal membrane stability in hemocytes. At co-exposure toxenobiotics and elevated temperature the number of hemocytes with nuclear abnormalities was increasedindicating the exceeding of organisms’ adaptive limits. Multivariate statistical analyses showed negative correlationsin pairs MT-SH/MT -Me and MT-SH/pyruvate and distinguished Gl and DcNfGl+T exposed groupsfrom other groups.
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