An investigation into the sensitivity of heat shock proteins as markers of cellular damage: a comparative study of hydrazine and cadmium chloride in primary rat hepatocyte cultures

Stress proteins have been proposed as markers of toxicity. This study investigated the sensitivity and specificity of stress proteins as markers of toxicity in primary hepatocyte cultures following exposure to two compounds, hydrazine and cadmium chloride (CdCl) . 2 Hepatocytes were exposed to increasing concentrations of hydrazine and CdCl for 2 h 2 and levels of the heat shock proteins HSP72/3, and HSP25 measured. In addition to this, ATP and GSH levels and LDH leakage were measured over the following 8 h. The results show that increasing concentrations of hydrazine caused dose-dependent decreases in ATP and GSH levels over 8 h. There was no change in the levels of HSP25 or HSP72/3 over that period. CdCl was found to significantly induce HSP72/3 at a concentration of 2 5 M when no other biochemical parameter was altered, levels were also elevated following administration of 10 M CdCl but ATP levels were found to be decreased at this 2 concentration. Levels of HSP25 were not increased following CdCl exposure at any 2 concentration. Higher concentrations of CdCl produced significant increases in LDH 2 leakage and depletion of intracellular levels of ATP and GSH. In addition to this levels of HSP25 and HSP72/3 were reduced to zero following administration of high concentrations of CdCl. In this study hydrazine does not induce either of the stress 2 proteins studied here whereas CdCl exposure causes the induction of HSP72/3 but not 2 HSP25. However it was determined that during the culture of primary hepatocytes basal levels of HSP25 and HSP72/3 were significantly increased when compared with levels determined in vivo. The results suggest that stress proteins may have the potential to be sensitive markers of toxicity in primary hepatocytes; however, the induction of individual stress proteins appears to be dependent upon the compound used. The apparent noninduction of the stress response by hydrazine and minor induction by CdCl might be 2 explained by the fact that whilst in culture the hepatocytes are under a continuous state of stress and therefore may not be able to elicit a full stress response following a chemical insult.