Ultrastructural alterations in the liver and intestine of carp Cyprinus carpio induced orally by ultra-low doses of endosulfan.

In order to elucidate the importance of food-borne chemical contamination in fish, cytological and ultrastructural alterations in hepatocytes and enterocytes of common carp Cyprinus carpio L. exposed for 5 wk to 0.5 microgram endosulfan (6,7,8,9,10,10-hexachloro-1,5,5a,6,9a-hexahydro-6,9-methano-2,4,3-benzo- dioxyanthiepin-3-oxide) kg-1 food dry weight, equivalent to an ultra-low dosis of 15 ng kg-1 fish d-1, were investigated by means of light and electron microscopy. Observations on liver alterations were quantified by morphometric analysis. Livers show enlargement of the nucleolus, increase in number and size of both Golgi fields and rough endoplasmic reticulum (ER) lamellae, as well as proliferation of peroxisomes and lysosomes. Taken together, these alterations represent the morphological equivalent of a general stimulation of hepatic metabolism. Proliferation of the smooth ER is indicative of the onset of biotransformation processes under the influence of food-borne endosulfan. Further pathological processes in the liver were evident by glycogen and lipid depletion, invasion of phagocytic macrophages, and accumulation of myelinated bodies in endothelial cells of hepatic sinusoids. In the intestinal tract, exposure to endosulfan is associated with a complete lack of chylomicrons in the epithelial lining, which indicates disturbance of intestinal absorption. The reaction of the gut epithelium also included considerable distension of the intercellular space and an elevated number of lysosomal inclusions in enterocytes. An increased rate of mucous cell precursors was detectable, and macrophages were numerous. Results are consistent with endosulfan resorption by the intestinal epithelium and the coexistence of gut and liver ultrastructural changes at extremely low doses. Thus, the substantiation of pathological alterations in organs sequentially in contact with toxicants appears useful as a biomarker of pollutant exposure and effect. With regard to a chemical spill into the Rhine river at Basel, Switzerland, in November 1986, endosulfan, as a component of the mixture of toxic substances, may well have contributed to the overall toxicity of the chemicals released during the accident and the subsequent fish kill, less as a toxicant in itself than as a stimulant for the toxicity of other xenobiotics.