Changes of cellular stress response related and transcript and Hsp70 protein levels in Siberian freshwater amphipods upon exposure to cadmium chloride in the lethal concentration range.

The induction of cellular stress response systems, heat shock protein /Hsp70 and multixenobiotic transporter , by cadmium chloride (CdCl) was explored in amphipod species with different stress adaptation strategies from the Lake Baikal area. Based on the lethal concentrations (LC) of CdCl, the sensitivities of the different species to CdCl were ranked (24 hr LC50 in mg/L CdCl (mean/95% confidence interval)): (1.7/1.3-2.4) < (2.9/2.1-4.0) < (5.7/3.8-8.7) < (18.1/12.4-26.6). Conjugated dienes, indicating lipid peroxidation, were significantly increased after 24 hr exposures to 5 mg/L CdCl only in the more CdCl-sensitive species and . Upon treatment with 0.54 to 5.8 mg/L CdCl for 1, 6 and 24 hrs, transcript levels were generally more increased after the longer exposure times and in the more CdCl-sensitive species. Relating the CdCl exposure concentrations to LCx values revealed that across the species the increases of transcript levels were comparatively low (up to 2.6-fold) at CdCl concentrations ≤LC50. Relative transcript levels were maximally increased in by 5 mg/L CdCl ( LC70) at 24 hrs (9.1-fold increase above the respective control). When was exposed to 5 mg/L CdCl ( LC90) for 24 hrs, the increase in was in comparison to considerably less pronounced (3.0-fold increase in levels relative to control). Upon exposure of amphipods to 5 mg/L CdCl, increases in Hsp70 protein levels compared to untreated controls were highest in at 1 and 6 hrs (5 mg/L CdCl LC70) and in at 24 hrs (5 mg/L CdCl LC45). Thus, when the fold increases in Hsp70 protein levels in the different amphipod species were related to the respective species-specific LCx values a similar bell-shaped trend as for transcript levels was seen across the species. Transcript levels of in CdClexposed individuals of the different amphipod species varied up to 4.7-fold in relation to the respective controls. In contrast to /Hsp70, transcripts in CdCl exposed individuals of the different amphipod species did not indicate similar levels of induction of at equal LCx levels across the species. Induction of and genes and Hsp70 proteins by CdCl in the lethal concentration range shows that these cellular responses are rather insensitive to CdCl stress in the examined amphipod species. Furthermore, the increase of expression of these cellular defense systems at such high stress levels suggests that induction of these genes is not related to the maintenance of normal metabolism but to mitigation of the effects of severe toxic stress.