Lysosomal changes in the response of molluscan hepatopancreatic cells to extracellular signals.

Marine mussels (Mytilus edulis, a bivalve mollusc) are increasingly used as environmental sentinels in pollution biomonitoring. Pathological reactions of the lysosomal system in hepatopancreatic cells have proven to be sensitive bioindicators of pollutant effect. However, if such reactions are to be used as biomarkers, then they must be clearly distinguishable from any hormonally-induced changes linked to normal seasonal activity such as the reproductive cycle. The aim of the present study was to test the effects of several cell-to-cell signalling compounds on the lysosomes of the hepatopancreatic digestive cells. In vitro incubation of tissue slices showed that epinephrine, acetylcholine and prostaglandin F2 alpha reduced lysosomal membrane stability and latency of beta-N-acetylhexosaminidase and beta-glucuronidase. These results indicate the presence of cell surface receptors for all three hormones. The observed changes in lysosomal fragility were less pronounced than those induced by pollutants and when considered together with other published data, indicate that hormonal regulation of digestive cell lysosomes is unlikely to pose a problem for the use of lysosomal reactions as biomarkers for chemical insult.