Cytochemical responses of the lysosomal system and NADPH-ferrihemoprotein reductase in molluscan digestive cells to environmental and experimental exposure to xenobiotics

Abstract

Lysosomal characteristics and smooth endoplasmic reticulum (SER) associated NADPHfernhemoprotein (cytochrome P-450) reductase were measured cytochemically in the digestive cells of mussels A4ytilu.s edulis and periwinkles Littorina littorea exposed to environmental contaminants In Langesundfjord, Norway (PAHs, PCBs, metals) and to xenobiotics in an experimental facility (diesel oil and copper mixture). Lysosomal membrane stability was reduced in both mussels and periwinkles with increasing xenobiotic contamination In the field. Lysosomal and cytoplasmic unsaturated neutral lipid concentration was increased in contaminated mussels in the field, and lysosomal accumulation was associated with enlargement of secondary lysosomes; the latter was inversely correlated with lysosomal membrane stability. hpofuscin content and number of tertiary lysosomes increased in contaminated field mussels. These pathological changes are indicative of enhanced lysosomal autophagy and fatty degeneration. NADPH-ferrihemoprotein reductase activity was elevated in mussels from the 2 most heavily contaminated field sites. Activity of this enzyme was directly correlated with total PAHs. Lysosomal data from experimental exposures were less clear and difficult to interpret. Poor nutritional conditions possibly masked pollutant effects. However, mussels from the highest exposure concentration showed elevated lipofuscin. The observed sensitivity of the tests for lysosomal enlargement and lysosomal lipid, combined with their relative simplicity, indicate their potential for the detection of environmentally induced pathology, although better understanding of the mechanisms of toxicity would enhance theu utility.