Divergent kinetics of hsp70 induction in Oniscus asellus (Isopoda) in response to four environmentally relevant organic chemicals (B[a]P, PCB52, gamma-HCH, PCP): Suitability and limits of a biomarker

Mature specimens of the isopod Oniscus asellus were maintained on soil and leaf litter to which was added different concentrations of either benzo[a]p yren (B[a]P), 2,2',5,5'-tetrachlorobiphenyl (PCB52), gamma-hexachlorocycloh exane (gamma-HCH), or pentachlorophenol (PCP) for a maximum of 14 days. Tim e-dependent investigation of the body level of the 70 kD stress protein gro up (hsp70) in the isopods revealed a significant but transient induction of the hsp70 response after about 24 h of exposure to PCB52 or B[a]P. Despite continuous exposure, the hsp70 level decreased subsequently and ended up c lose to or below the control level independent of the concentration of PCB5 2 or B[a]P in the substrate. All applied PCP or gamma-HCH concentrations al so resulted in an initial peak of hsp70 response after 24 h of exposure and a second peak after several days of exposure, as well as an elevated hsp70 level throughout the period of exposure. Although acute stress conditions posed by all four organic chemicals were monitored by stress protein induct ion, hsp70 can act as a biomarker of chronic exposure and effect for PCP an d gamma-HCH only.