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(22-54) Model slugs to investigate the role of calcium cells in adaptation to chronic metal-pollution. Zaldibar, Beņat*,1, Iturralde, Josune1, Cancio, Ibon1, Marigomez, Ionan1, 1 Dept. of Zoology and Animal Cell Dynamics. Univ. Basque Country., Bilbo., Basque Country (Spain) ABSTRACT- The digestive gland of marine molluscs is the main organ involved in accumulation and detoxification of environmental pollutants. The epithelium of the digestive tubules is composed by two cell types, digestive and basophilic cells. Under normal physiological conditions digestive cells outnumber basophilic cells, but under different stress situations the composition of the epithelium changes basophilic cells replacing digestive ones. Marine winkles Littorina littorea were exposed to 1.25 mg/l Cd for 21 days to provoke the proliferation of basophilic cells. Then, animals were depurated in clean seawater for 10 days to determine whether cell-type replacement was reversible. Digestive glands were fixed in Carnoy and paraffin embedded for histological analysis. Quantification of basophilic cells applying stereological techniques on haematoxylin-eosin stained sections, showed increased relative number of basophilic cells in Cd exposed animals. The basophilic to digestive cells ratio returned to usual values after the depuration period. Autometallography (AMG) revealed the presence of Cd in digestive cell lysosomes whereas basophilic cells appeared devoid of AMG deposits. After depurating, AMG deposits distributed differently and clear areas corresponding to basophilic cells were less conspicuous. Changes occurring in the lysosomal compartment were quantified by automated image analysis on cryostat sections stained histochemically for the demonstration of Key words: molluscs, cell-type replacement, recovery, cadmium |
-glucuronidase activity. In this case, enlarged lysosomes were observed in stressed animals while return to control levels occurred in depurated animals. Finally, we performed PCNA immunohistochemistry to demonstrate whether changes in the digestive to basophilic cells ratio were due to proliferation of basophilic cells upon exposure to Cd and to proliferation of digestive cells upon depuration. *Work Funded by Basque Government (PI-1999-23).