Detection of P-glycoprotein mediated MDR/MXR in Caranus maenas hepatopancreas by immuno-gold-silver labeling

Carcinus maenas were sampled in the German Bight for immunohistochemistry, histology and parallel chemical analysis of organochlorines. Incubations were performed with a monoclonal antibody against P-glycoprotein which mediates multixenobiotic resistance in order to investigate whether Carcinus maenas develop MXR in hepatopancreas. The data showed that MXR was highly expressed at the microvilli of epithelial cells while inside epithelial cells of the tubules MXR was restricted to a specific cell type, the transitional stage between fibrillar (F) cells and blister (B) cells. These cells were rich in lysosomes as was demonstrated by high acid phosphatase activity. In aging B cells, fusion events of the lysosomal compartment to one large vacuole were observed to be accompanied by a loss of MXR protein content. Subsequently, B cells were eliminated from the epithelium into the lumina where the cell debris was incorporated into the faeces. It is concluded that F/B cells appear to be specialized for accumulation of toxic compounds and their digestion and elimination.