Investigation of cellular stress response related heat shock protein hsp70/Hsp70 and multixenobiotic transporter abcb1 in Siberian freshwater amphipods upon cadmium exposure

Abstract

Induction of stress response genes hsp70 and abcb1 and Hsp70 protein by cadmium chloride (CdCl2) was explored in amphipod species with different stress adaptation strategies from the Lake Baikal area. Based on lethal concentrations (LC) the sensitivities to CdCl2 were ranked (24 hr LC50 - mg/L CdCl2): Gammarus lacustris (1.7) < Eulimnogammarus cyaneus (2.9) < E. verrucosus (8.3) < E. vittatus (18.2). Conjugated dienes indicating lipid peroxidation were significantly increased by 5 mg/L CdCl2 (24 hr exposure) only in G. lacustris and E. cyaneus. Upon treatment with 0.54 - 5.8 mg/L CdCl2 hsp70 transcript levels were more increased in the toxicologically more sensitive species. Relating the exposure concentrations to LCx values revealed that across the species the increases of hsp70 transcript levels were comparatively low (up to 2.6-fold) up to LC50; at higher LCx values hsp70 induction was more pronounced (up to a 9.1-fold by 5 mg/L CdCl2 ([wedgeq]LC70) in E. cyaneus). In contrast, abcb1 inductions did not correspond with CdCl2 LCx values across species; abcb1 induction was highest (4.7-fold) in E. verrucosus by 5.0 mg/L CdCl2 ([wedgeq]LC45, 24 hr exposure). Induction of stress gene responses by lethal CdCl2 concentrations indicates that in the amphipods they are rather insensitive.