Use of polyclonal antibodies for the detection of changes induced by cadmium in lysosomes of aquatic organisms.

Lysosomal responses are widely accepted cellular effect biomarkers of general stress. Up to now, these biomarkers have been analysed by means of conventional techniques based on enzyme histochemical methods, where lysosomal enzymes such as acid phosphatase and beta-glucuronidase (beta-GUS) have been employed as markers of lysosomes. The aim of the present work was to develop more advanced and sensitive methods based on the use of polyclonal antibodies to measure lysosomal enzymes in different sentinel organisms. For this purpose, we have studied the cross-reactivity of two commercial polyclonal antibodies against the lysosomal enzymes acid phosphatase and beta-GUS with molluscan digestive gland by means of immunoblotting and immunohistochemistry. The antibody against acid phosphatase cross-reacted specifically with the lysosomal fraction of the digestive gland, while unspecific immunoreaction occurred with digestive gland whole homogenates and tissue sections. The antibody against beta-GUS cross-reacted specifically with digestive gland whole homogenates and tissue sections. The cross-reactivity of this antibody was tested also in crab hepatopancreas and mullet liver where the same successful results were obtained. The second aim of the present study was to test if the immuno-based approach was sensitive enough to detect lysosomal alterations provoked by contaminants. For this purpose two experiments were carried out with mussels treated with cadmium in two ways: in vivo treatment by injection and in vitro treatment using digestive gland explants. Afterwards immunoblotting studies with the antibody against beta-GUS were applied and immunoreactive bands were quantified by means of a gel analysis programme. We found that beta-GUS protein levels were higher in treated mussels when compared with controls in either in vivo or in vitro treatments. All these data suggest that the polyclonal antibody against beta-GUS is adequate to be used in immuno-based approaches to detect contaminant-induced lysosomal alterations.