Field validation of hsp70 stress proteins as biomarkers in Asian clam (Potamocorbula amurensis): Is downregulation an indicator of stress?

The focus of this paper is to consider the applicability of the hsp70 stress protein response as a biomarker in field studies. Stress proteins (or heat shock proteins, hsp) of the hsp70 family are induced by sublethal concentrations of a variety of environmental pollutants. However, few studies have applied these proteins as biomarkers of environmental stress under field conditions. Our laboratory is investigating hsp70 proteins and other responses of Asian clam (Potamocorbula amurensis) as potential biomarkers in laboratory and field studies. Our efforts include two studies presently being conducted in northern San Francisco Bay: (1) monthly collection of clams from four sites along a cadmium contamination gradient; (2) 7 day in situ exposure of clams at two selected sites at Mare Island Naval Shipyard. Here we present results on hsp70 proteins in P. amurensis in field-collected and outplanted clams. Both field projects are ongoing, therefore the results presented here do not represent completed studies; rather, they illustrate a portion of our experience. For this workshop, we illustrate weaknesses and strengths of these proteins as biomarkers, and we underscore where additional work is needed. In field-collected clams (study no. 1), site-specific differences in levels of two hsp70 proteins, hsp70 and hsp76, were measured in May and June 1997. Although an inverse correlation exists between cadmium tissue concentrations and hsp70 protein levels, differences detected may be reflective of a salinity gradient. Results from recent laboratory exposures to cadmium and a range of salinities are discussed. After in situ exposure for 7 days (study no. 2), both hsp70 and hsp76 levels were significantly reduced in clams from site R. However, given a brief heat-shock in the laboratory, hsp70 protein levels were significantly higher in clams from this site than in controls. Results indicate that downregulation as well as upregulation of hsp70 proteins may be indicators of stress in P. amurensis.

Duke Scholars

Author David E. Hinton Environmental Sciences and Policy