Testicular damage after exposure to carbendazim depends on the number of patent efferent ductules.

To study how long-term testicular damage depends on the patency of the efferent ductules (EFDs), rat testes and epididymides were examined after a single exposure to carbendazim (methyl 2-benzimidazole carbamate; MBC). The number of patent EFDs was determined in sections of the caput epididymides at 8, 16, 32 and 70 days post-treatment, and the testes were grouped into the following categories: those with intact EFDs, those with partially patent EFDs, or those with totally occluded EFDs. In each testis, 100 seminiferous tubules were examined for the presence of abnormalities. The mean weight of testes with partially patent EFDs was significantly higher compared with the control, whereas that of testes with totally occluded EFDs was significantly lower. Histologically, most seminiferous tubules of the testes with intact EFDs were normal. The testes with partially patent EFDs contained normal, degenerative and atrophic seminiferous tubules at various frequencies depending on the number of patent EFDs, and it was evident that as the number of patent EFDs increased, the number of normal seminiferous tubules also increased at any interval. In these testes, the number of normal seminiferous tubules increased progressively as the post-treatment interval increased, irrespective of patency of the EFDs. In the testes with totally occluded EFDs, atrophic seminiferous tubules were the most numerous. These results indicate that whether or not the testis is able to survive the long-term deleterious effects of MBC depends largely EFD patency.