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 i n fish, cytological and ultrastructural alterations in hepatocytes and ente rocytes of common carp Cyprinus carpio L. exposed for 5 wk to 0.5 mu g endo sulfan (6,7, 8, 9, 10, 10-hexachloro-1,5, 5a, 6, 10-hexahydro-6, 9-methano- 2,4,3-benzo-dioxyanthiepin-3-oxide) kg(-1) food dry weight, equivalent to a n 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 quan tified by morphometric analysis. Livers show enlargement of the nucleolus, increase in number and size of both Golgi fields and rough endaplasmic reti culum (ER) lamellae, as well as proliferation of peroxisomes and lysosomes. Taken together, these alterations represent the morphological equivalent o f a general stimulation of hepatic metabolism. Proliferation of the smooth ER is indicative of the onset of biotransformation processes under the infl uence of food-borne endosulfan. Further pathological processes in the liver were evident by glycogen and lipid depletion, invasion of phagocytic macro phages, and accumulation of myelinated bodies in endothelial cells of hepat ic sinusoids. In the intestinal tract, exposure to endosulfan is associated with a complete lack of chylomierons in the epithelial lining, which indic ates disturbance of intestinal absorption. The reaction of the gut epitheli um also included considerable distension of the intercellular space and an elevated number of lysosomal inclusions in enterocytes. An increased rate o f mucous cell precursors was detectable, and macrophages were numerous. Res ults 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 s equentially in contact with toxicants appears useful as a biomarker of poll utant exposure and effect. With regard to a chemical spill into the Rhine r iver 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 f ish kill, less as a toxicant in itself than as a stimulant for the toxicity of other xenobiotics.