Epithelial reorganization and irregular growth following carbendazim-induced injury of the efferent ductules of the rat testis

Occlusions of the rat efferent ductules were induced by an oral gavage of carbendazim and the capacity for regeneration or recanali- zation of the ductules was histologically evaluated between 2 and 70 days post-treatment. At 2 days post-treatment, the efferent ductules were oc- cluded by sloughed materials and showed various degrees of inflammation. Severely damaged epithelium showed few regenerative features at later intervals. On the other hand, epithelia with medium inflammation often exhibited irregular epithelial growth along the luminal contents or the for- mation of multiple abnormal ductules. These abnormal ductules were formed by migrated and original epithelia at the periphery of the occluded lumen at 16 days post-treatment, indicating attempted recanalization. At later time periods, 32 and 70 days post-treatment, the occluded original lumen was filled in by fibrotic connective tissue and surrounded by a series of abnormal ductules. These abnormal ductules were characterized by cuboidal epithelia, a small luminal diameter, fewer cilitated cells than nor- mal, less developed organelles in the epithelial cells, and basal laminae of irregular thickness. However, there was no evidence that occluded ductules formed patent re-connections via abnormal ductules. The results suggest that occluded efferent ductules have the ability to initiate epithelial regrowth and to form new ductules, but the newly formed ductules are abnormal and are not adequate to recover from azoospermia at least at 70 days post-treatment. Key words: Abnormal epithelial growth, Efferent ductules, Microcanals