THE ANATOMICAL RECORD 2355-60 zy (1993) zy Epithelial Reorganization and Irregular Growth Following Carbendazim-Induced Injury of the Efferent Ductules of the Rat Testis MASAAKI NAKAI, BILLY J. MOORE, AND REX A. HESS zyxw Department zyxwvutsrq of Veterinary Biosciences, University of Illinois, Urbana, Illinois 61801 (M.N.,B.J.M.,R.A.H.); Department of Veterinary Anatomy, Faculty of Agriculture, Miyazaki University, Miyazaki 889-21, Japan (M.N.) zyxw ABSTRACT 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, o zyxwv 1993 Wiley-Liss, Inc. Occlusion, Carbendazim, Rat Epithelia of tubular organs may respond to injury in several ways. The epithelial cells may die after exhib- iting stages of the apoptotic process; the cells may slough away from the basement membrane leaving be- hind basal lamina andlor connective tissue; or some cells may survive the injury, dedifferentiate, enter mi- tosis, andlor flatten and regrow a new epithelium (Siege1 and Bulger, 1975; van Hattum et al., 1979; Keenan et al., 1982; Bowden and Adamson, 1985; Bas- sett et al., 1986; Freund et al., 1989; Tanner and Evan, 1989; Gobe et al., 1990; Madri, 1990). Epithelial re- sponses in tubular organs to injury are often compli- cated by the type of injury and post-injury reactions of the connective tissue (Basset et al., 1986; Madri, 1990; Thompson, 1990). Except for the well-established re- quirement that the underlying connective tissue orga- nization must remain intact for normal regeneration of an epithelium (Madri, 1990; Thompson, 19901, little is known regarding the mechanisms of epithelialization of an injured tubular organ. Responses of epithelial tissue to injury have been studied in several different types of tubular organs; zyxwv 0 1993 WILEY-LISS, INC. however, only limited information is available on the male reproductive system. In the male, studies have focused primarily on the long-term effects of vasectomy. It appears that the ligated vas deferens is capable of generating new channels that, in some cases, may re- connect the two severed ends of the duct, permitting the passage of sperm from the epididymis into the ejaculate semen. This unusual phenomenon is called “recanali- zation” or micror re canalization^' (Civantos et al., 1972; Freund and Couture, 1982; Hayashi et al., 1983;Cruick- shank et al., 1987; Freund et al., 1989). Obstructive lesions in the head of the epididymis have also been associated with the process of recanalization (Cooper and Jackson, 1973; Ball and Mitchinson, 1984; Hess et al., 1991; Nakai et al., 1992). However, these reports of terminal lesions have provided little under- Received April 10, 1992; accepted May 21, 1992. Address reprint requests to Dr. Rex A. Hess, Department of Veter- inary Biosciences, 2001 South Lincoln Avenue, Urbana, IL 61801.