Effects of testosterone enanthate on the structure of the male reproductive tract of the rat

The histology and fine structure of the testis, epididymis and sex accessory glands were studied in young adult male rats administered testosterone enanthate, 120 μg/100 g body weight, three times weekly for 4, 8, or 12 weeks. The weights of the testis and epididymis decreased, and animals treated for 11 weeks were infertile. Alterations were found in the seminiferous tubules of all rats treated for 8 or 12 weeks, including the presence of many degenerating germ cells and a-large decrease or absence of late spermatids. Study of different stages of the cycle of the seminiferous epithelium showed that the greatest number of degenerating germ cells, step 7 spermatids and pachytene primary spermatocytes, occurred at stages VII-VIII of the cycle. Some normal appearing spermatogonia, primary spermatocytes and early spermatids remained in most seminiferous tubules. Sertoli cells contained many lipid droplets and lysosome-like bodies, and degenerating cells were surrounded by Ser-toli cell cytoplasm. The Leydig cells of treated animals were greatly reduced in size. Sperm progressively disappeared from the lumen of the middle segment and proximal part of the terminal segment of the epididymis after treatment for 8 or 12 weeks. Changes in the middle segment also included the appearance of intraepithelial cavities containing debris, and the presence within the epithelium of phagocytic cells that resembled leukocytes. The lumen of the proximal part of the terminal segment was often collapsed, while in the distal part of the terminal segment, the lumen was filled with cellular debris and degenerating sperm. Organelles of the principal cells of the epididymal epithelium appeared to be qualitatively unaltered. The weight of the sex accessory glands remained close to normal, and the presence of normal ultrastructural features suggested that production of secretions continued.     

Immunohistochemical detection of macrophage migration inhibitory factor in fetal and adult bovine epididymis: release by the apocrine secretion mode?

Originally defined as a lymphokine inhibiting the random migration of macrophages, the macrophage migration inhibitory factor (MIF) is an important mediator of the host response to infection. Beyond its function as a classical cytokine, MIF is currently portrayed as a multifunctional protein with growth-regulating properties present in organ systems beyond immune cells. In previous studies, we detected substantial amounts of MIF in the rat epididymis and epididymal spermatozoa, where it appears to play a role during post-testicular sperm maturation and the acquisition of fertilization ability. To explore its presence in other species not yet examined in this respect, we extended the range of studies to the bull. Using a polyclonal antibody raised against MIF purified from bovine eye lenses, we detected MIF in the epithelium of the adult bovine epididymis with the basal cells representing a prominently stained cell type. A distinct accumulation of MIF at the apical cell pole of the epithelial cells and in membranous vesicles localized in the lumen of the epididymal duct was obvious. In the fetal bovine epididymis, we also detected MIF in the epithelium, whereas MIF accumulation was evident at the apical cell surface and in apical protrusions. By immunoelectron microscopy of the adult bovine epididymis, we localized MIF in apical protrusions of the epithelial cells and in luminal membrane-bound vesicles that were found in close proximity to sperm cells. Although the precise origin of the MIF-containing vesicles remains to be delineated, our morphological observations support the hypothesis that they become detached from the apical surface of the epididymal epithelial cells. Additionally, an association of MIF with the outer dense fibers of luminal spermatozoa was demonstrated. Data obtained in this study suggest MIF release by an apocrine secretion mode in the bovine epididymis. Furthermore, MIF localized in the basal cells of the epithelium and in the connective tissue could be responsible for regulating the migration of macrophages in order to avoid contact of immune cells with spermatozoa that carry a wide range of potent antigens.     

Permeability of the diaphragmatic mesothelium: The ultrastructural basis for “stomata”

The ultrastructure of the hamster efferent ducts and epididymis was studied and the results were correlated with previously published data on the composition of luminal fluid obtained by micropuncture. Samples of the efferent ducts and parts of the epididymis designated initial segment, caput, corpus, proximal cauda, distal cauda, and “epididymal vas” were prepared. The efferent ducts contained principal cells characterized by a profusion of apical vesicles and numerous very large vacuoles that were distributed throughout the cytoplasm. Ciliated cells had few vesicles and vacuoles. Occasional cells contained many particles resembling glycogen. In the epididymis, the following trends were observed. The height of the epithelium and the size of the principal cells declined from initial segment to distal cauda. Apical vesicles and vacuoles with a light content were extremely numerous in principal cells of the initial segment and decreased progressively in the more distal regions. In the initial segment, basal and perinuclear rough endoplasmic reticulum was abundant and was distended with a material that resembled newly synthesized protein. Further distally in the epididymis cisternae of the rough endoplasmic reticulum were narrow and contained little intracisternal material. Light cells containing many vesicles, vacuoles, and lysosome-like structures were very prominent in the caudal segments. The epithelium of the epididymal vas had features intermediate between cauda epididymidis and ductus deferens. The cytoplasmic droplet in luminal sperm began to migrate caudally between the caput and corpus epididymidis and reached the posterior extremity of the middle piece in the distal cauda. Some degenerating sperm were observed in the lumen of the distal segments of the epididymis. The abundance of cytoplasmic vesicles and vacuoles in principal cells of the efferent ducts and initial segment of the epididymis correlated with the site of greatest fluid absorption as determined by micropuncture studies, suggesting that these structures are involved in absorption of fluid from the lumen. Between the caput and distal cauda epididymal segments, where absorption of sodium and potassium but not of fluid occurred, there were few vesicles and vacuoles in principal cells, but the “light” cells were large and numerous and contained many vacuoles. The principal cells of the initial segment were best equipped with rough endoplasmic reticulum to synthesize a protein.     

Morphologic evaluation of the effect of long-term administration of ammonium fluoride on the seminiferous epithelium and epididymis in the rat

Male rats were subjected to 9-month-long exposure to ammonium fluoride. The performed evaluation covered the seminiferous epithelium and epididymis. The greatest changes in animals used in the experiment were observed in epididymis. A small number of spermatozoa were seen in the lumen of ductus epididymis, while in the epithelial cells there were increased phagocytic processes, providing a proof that injured reproductive cells were eliminated from the genital tract.     

The influence of progestin and androgen on the fine structure of the male reproductive tract of the rat. II. Epididymis and sex accessory glands

Young adult male rats were administered medroxyprogesterone (Provera, Upjohn) alone and in combination with testosterone, as has been done to inhibit male fertility. The histology and fine structure of several segments of the epididymis, the ventral prostate, and the seminal vesicle were studied at intervals after treatment for up to 16 weeks. The epididymides of treated animals weighed less than those of control rats. Microscopic alterations in the epididymis were similar in rats treated with Provera alone and in those animals that received Provera and testosterone, but the changes varied with the segment of the epididymis. In the middle segment in the caput epididymidis, the normally abundant luminal sperm were absent but the epithelium retained its normal ultrastructural features. In the terminal segment in the cauda epididymidis, different changes were observed in the proximal and distal portions. In the proximal cauda epididymidis, the lumen was small, irregular in outline, and virtually devoid of sperm. The light cells of the epididymal epithelium in the proximal cauda contained extremely large numbers of dense bodies resembling lysosomes, which occupied most of the supranuclear and basal cytoplasm. In contrast, in the distal part of the cauda epididymidis, the epithelium had a normal appearance but the lumen was filled with debris, sperm, and spherical masses of cytoplasm that were apparently derived from germ cells. It is suggested that the clearing of the lumen of the proximal cauda epididymidis may reflect the greater activity of light cells of the epididymal epithelium in that region. Although alterations in spermatogenesis may be most important in the antifertility effect of progestin and androgen, these alterations in epididymal sperm and epithelium may also play a role. The weights of the prostate and seminal vesicles of rats treated with Provera (1 mg/100 g/day) were greatly reduced compared to those of control rats. Although there was considerable variation, in many specimens treated with Provera alone the epithelium of the prostate showed a change from a columnar to a cuboidal or squamous shape, and there was a reduction in the size and abundance of organelles involved in the formation of secretions. The microscopic structure of the seminal vesicle of rats treated with Provera was less severely affected than the prostate. Although the seminal vesicle epithelium of Provera-treated rats was generally not as tall as in control animals, the cells possessed parallel cisternae of rough endoplasmic reticulum, secretory vacuoles, and an active-appearing Golgi apparatus, suggesting that they continued to be able to form secretions in the presence of Provera. The weights of the sex accessory glands were maintained at control levels by the administration of testosterone, 100 μg/100 g/day, along with the Provera. A normal fine structure was present in the epithelium of both the prostate and seminal vesicle of rats administered this amount of testosterone in addition to Provera. Lower doses of testosterone (15 or 30 μg/100 g/day) were insufficient to maintain normal weight or ultrastructure of the sex accessory glands in the presence of Provera.     

Reproduction in the male honey possum (Tarsipes rostratus: Marsupialia): The epididymis

The epididymis of the adult honey possum, Tarsipes rostratus, is enclosed by a heavily pigmented tunica vaginalis and lies with the testis in a prominent prepenile scrotum. It is connected to the testis by a single ductus efferentis and is lined by approximately equal numbers of cuboidal ciliated and principal cells. It is unusual for marsupials in having no well-defined compartments or fibrous septae and in having extensive convolutions of the duct only at the caudal flexure. Three principal functional zones (initial, middle, and terminal segments) were identified in the epididymis, based on epithelial type and ultrastructural evidence of sperm maturation. Luminal diameter increases progressively throughout the tract, and epithelial height variations (from about 2 to 20 μm) are greatest in the terminal segment. The epithelium itself is remarkably low (maximum of 21.6 μm) compared with that seen in the epididymis of other mammals. The thickness of the peritubular smooth muscle coat increases close to the junction of the epididymis and ductus deferns. Sperm concentrations were estimated from counts of sperm nuclei and thus can be no more than approximations. The figures are consistent, however, with a rapid increase in concentration in the initial segment, indicating extensive fluid resorption. Sperm concentrations appear to peak in the distal zone of the terminal segment, although sampling problems and wide variations in count make such a conclusion only tentative. Principal and basal cells are the predominant cell types in the epididymal epithelium. Basal cells are most abundant in the initial and distal middle segment. Principal cells show structural evidence of active exchange with the luminal contents and have abundant apical stereocilia, the structure of which depends on the epididymal zone. Other cell types occur less commonly in the epithelium. Lipid-rich and phagocytic principal cells are restricted to the middle and distal zones of the middle segment, respectively. Clear cells, restricted to the terminal segment, and halo cells were found in very low numbers. As in some other marsupials, principal cells (possibly specialized for this function) selectively remove cytoplasmic droplets and probably other cellular debris from the luminal contents. In Tarsipes, however, this process is not very efficient, and many discarded droplets pass through to the terminal segment where they form large masses of debris associated with aggregates of degenerating spermatozoa.     

低剂量棉酚与激素联合应用的抗生育作用位点的研究

目的 探讨低剂量棉酚与激素联合应用在8周内使大鼠达到不育效果的作用位点.方法 本实验采用大鼠喂服棉酚12.5mg/(kg·d) 去氧孕烯125μg/(kg·d) 炔雌醇25μg/(kg·d) 十一酸睾丸酮100mg/(kg·d)的联合用药方式,与单独喂服相同剂量的棉酚或激素的大鼠及喂服载体溶剂的大鼠相对照,通过一系列形态学观察和半定量检测,探讨联合用药的具体作用环节.结果 无论在睾丸组织形态还是睾丸精子数量,联合用药组的变化趋势都与单独应用激素组的相似,而不同于单独应用棉酚组和对照组.而在附睾中,3个用药组在精子活力和精子形态方面,都与对照组有显著差异.结论 联合用药组中激素主要使睾丸精子数量迅速下降;而在精子数量大大下降的基础上,棉酚和激素又对已成熟精子的结构和运动能力进一步破坏,从而使雄性大鼠受精能力迅速下降,联合用药组比单独应用其中一种成分更快、更有效地达到使大鼠不育的目的.     

A Study of Effect of Progesterone on Epididymis in Albino Rats

Progesterone, an anti androgen compound that recently receiving attention for potential use as male contraceptive and for other medical purposes, such as treatment of prostate diseases. In the present study adult male albino rats were administered the progesterone for 15 &; 30 days and the histology and fine structures of the epididymis were studied. After treatments for 15 and 30 days sperms were found to greatly reduce in number from lumen of caput epididymis, middle segment and cauda epididymis, of severely affected specimen. The epithelium was tall and the light cells were large and distended with many dense bodies resembling lysosome (Loving &; Flickinger 1976)1. The lumen was filled with scanty sperm and debris, which appears to be derived from germ cells. It is suggested that the light cells of epididymal epithelium may have a role in clearing the lumen in which they are particularly large and numerous.The aim of present study is to determine the effect of progesterone on the structure of target cells of epididymis normally stimulated by androgens and further correlate the findings in light of previous studies, to draw the significant conclusion. The study showed that the progesterone have intense inhibitory effect on the epididymis. The degenerative histological findings are found in form of reduce number of spermatozoa, debris of cell mass &; reduce epithelial cells height. These changes may have an important role in the anti fertility effect of progesterone.     

癫痫对雄性大鼠睾丸及附睾组织病理学和超微结构的影响

目的：探讨癫痫发作对雄性Wistar大鼠睾丸及附睾组织病理和超微结构的影响。方法：运用氯化锂一匹罗卡品建立Wistar雄性大鼠癫痫模型,取睾丸、附睾分别制片观察组织病理及超微结构的形态学改变。结果：光镜观察下,A组（造模成功组）及B组（造模不成功组）大鼠睾丸生精小管内各级生精细胞排列基本整齐,结构未见明显紊乱现象,但生精细胞层次呈不同程度的减少,睾丸生精小管管腔内精子数目减少,可见坏死脱落的生精细胞,睾丸间质结构缺如,间质细胞明显减少。附睾中,A组管壁柱状细胞,基细胞层次清晰,结构整齐,微绒毛排列整齐,但管腔中精子数目明显减少,有较多的非精子细胞成分。B组附睾管腔中精子数目未见明显下降,有时可见散在的生精细胞。电镜观察下,A组大鼠睾丸生精细胞细胞核明显畸形,线粒体肿胀,线粒体膜仍然完整,但脊消失,粗面内质网肿胀明显,精子头部细胞核清晰,顶体形态不规则,尾部“9＊2＋2”结构整齐,周围包绕的线粒体鞘明显肿胀,线粒体数目明显减少。B组中仍可见上述不同程度的损害表现,附睾中,A组及B组均可见处于同一层面的主细胞,细胞核未见明显异常,核周围可见大量溶酶体,同时核周内质网均处于明显肿胀状态。C组（正常对照组）鼠睾丸及附睾切片的光镜、电镜表现皆正常。结论：癫痫不同程度的发作可引起大鼠睾丸及附睾组织病理和超微结构不同程度的改变,进而造成了雄性Wistar大鼠生殖系统相关指标的改变。     

The ultrastructural pathology of the rat epididymis after administration of α-chlorhydrin (U-5897). I. Effects of a single high dose

The ultrastructural pathology of the initial segment of the rat caput epididymidis was examined after oral administration of a single high dose of the antifertility compound α-chlorhydrin (U-5897) at time intervals ranging from two hours to nine days after treatment. At doses in excess of 30 mg/kg this compound produces a lesion specifically localized in the initial segment of the epididymis characterized by sloughing of the epithelium, which leads to obstruction of the lumen of the epididymal duct, spermatocoel and sperm granuloma formation and an ultimate occlusive fibrosis. In rats fed 140 mg/kg of U-5897 the first effects can be seen as early as two hours after treatment. Within 48 hours after treatment, the lumen of the greater part of the initial segment is filled with degenerating cells and debris which block further passage of sperm along the duct. The present study provides insight into the nature of the early events in the evolution of this epididymal lesion. Possible mechanisms of action of α-chlorhydrin are discussed.     

Selenium provides protection to the liver but not the reproductive organs in an atrazine-model of experimental toxicity

The present study evaluated the possible protective effects of selenium against atrazine-induced toxicity in the liver and reproductive system of rats. Atrazine administered to rats orally at a dose of 120 mg/kg caused an inhibition in the activity of glutathione-S-transferase and an increase in malondialdehyde formation in the liver, testis and epididymis. Superoxide dismutase decreased in the liver and testis but was increased in the epididymis. Furthermore, hepatic glutathione and lactate dehydrogenase activity increased while epididymal catalase, ascorbate content, hepatic aspartate aminotransferase and glutathione peroxidase activities in all the tissues decreased in the atrazine-treated animals. Hepatic, testicular and epididymal alanine aminotransferase activities were not affected by atrazine (p>0.05). Decreased epididymal and testicular sperm number, sperm motility, daily sperm production and increased number of dead and abnormal sperm were observed in atrazine-treated rats.Treatment of rats orally with selenium at a dose of 0.25 mg/kg did not prevent atrazine-induced changes in sperm characteristics and had no protective effects against atrazine-induced biochemical alterations in the testis and epididymis except testicular lactate dehydrogenase. Catalase activity and ascorbate contents were unchanged in these groups of animals. However, selenium effectively protected against atrazine-induced changes in biochemical indices in the liver. In rats treated with selenium alone, glutathione peroxidase in all the tissues, hepatic glutathione and superoxide dismutase, testicular lactate dehydrogenase activity and ascorbate content increased, while hepatic catalase activities decreased (p<0.05).Our data suggest that selenium effectively attenuated the toxic effects of atrazine-induced liver changes but not in the reproductive organs and sperms of rats. Selenium might therefore be useful in ameliorating oxidative stress in the liver.     

Studies on prolonged spermatozoa survival in chiroptera: A morphological examination of storage and clearance of intrauterine and cauda epididymal spermatozoa in the bats Myotis lucifugus and M. velifer

The cauda epididymidis, uterine corpus, and cornua and uterotubal junction of Myotis function to retain and preserve normal spermatozoa throughout hibernation. In none of the sites do spermatozoa show features that might account for their extended viability. Spermatozoa stored in the uterus and epididymis show no special orientation toward the epithelium lining these sites, whereas an intimate relationship is established between some sperm and the epithelial cells of the uterotubal junction which might either account for extended postcoital sperm survival or forecast their removal from further participation. Transmission and scanning electron microscopic observations do not disclose any morphological changes in stored luminal spermatozoa. A low rate of phagocytosis of sperm is evident in the female tract during hibernation. However, spermatozoa are evidently not vulnerable to being removed from the storage sites until spring arousal when ovulation occurs. Both uterotubal epithelial cells and phagocytes appear to be involved in the disposal of spermatozoa in the female, whereas epididymal spermatozoa apparently are primarily voided during urination. A mechanism that delays capacitation must underlie the ability of spermatozoa to survive in the female reproductive tract of the hibernating bat.     

Reproductive abnormalities in canine fucosidosis

Male English springer spaniel dogs affected with fucosidosis, a lysosomal storage disorder, were found to be infertile while females with the disease reproduced successfully. Ejaculates of semen collected from affected dogs had reduced total sperm output and morphologically abnormal spermatozoa. A high proportion of ejaculated spermatozoa had midpiece droplets, bent tails and poor motility. Severely vacuolated epididymal epithelial cells were observed by light microscopy. Electron microscopic examination revealed membrane-bound vacuoles of variable size containing scanty amounts of granular to fibrillar material in epididymal epithelial cells, smooth muscle, myoid cells and Sertoli cells. Male infertility is believed to result from lysosomal storage of fucosyl-linked substrates in cells of the reproductive system. The extensive lesions in the epididymis may have interfered with maturation and transport of spermatozoa. Also, deficiency of alpha-L-fucosidase activity could have impaired the shedding of cytoplasmic droplets from spermatozoa and altered the surface glycoprotein composition of the sperm during epididymal transit.     

Experimental dapsone administration induces infertility in male Wistar rats: Mechanisms and clinical implications

Dapsone (4, 4′-diaminodiphenylsulfone, DDS) is a potent anti-inflammatory and antibacterial compound which has been used in the treatment of leprosy, vasculitis and dermatitis herpetiformis, lupus erythematosus profundus and even as an antimalarial in combination with proguanil. This study investigated the effect of the administration of dapsone on the reproductive activities of male rats using in vivo and in vitro techniques. In the in vivo study, dapsone was administered orally to male Wistar rats for 5 days or 6 weeks after which their body weight, relative reproductive organ weights, sperm parameters and reproductive hormones were determined while testicular and epididymal histology were also assessed. Data were compared using analysis of variance and Students-Newman-Keuls multiple comparison test. For the in vitro study, Sertoli cells were cultured and treated with varying doses of dapsone at different durations, thereafter Sertoli cell viability and nuclei integrity were determined. Also, the genetic expressions of Glial cell line-derived neurotrophic factor (GDNF) and transferrin were assessed. The results obtained from the in vivo study showed a duration-dependent significant decrease in body and reproductive organ weights, sperm parameters and serum testosterone concentration. Testicular and epididymal histology also showed duration-dependent degenerative changes. However, all these changes were restored towards control values in the recovery experiment. The viability and deoxyribonucleic acid (DNA) integrity of the treated Sertoli cells showed dose and duration-dependent adverse effects while GDNF and transferrin showed normal genetic expressions. These results suggest that dapsone could induce male reproductive stress by affecting testicular and epididymal structure and function.     

Changes in lectin-binding sites on epididymal cells during postnatal development of the mouse

Using lectin histochemistry combined with immunohistochemistry, we recently demonstrated that the principal, clear, and basal cells in the adult mouse epididymis specifically react with UEA-I, MAL-I, and GS-IB lectins, respectively. The present study examined the distribution of the lectin-binding sites for some lectins on the epididymal epithelium during postnatal development. Galactose staining with GS-IB was first detected in some of the undifferentiated epithelial cells in mice aged 1 week, and this characteristic became specific to basal cells in mice aged 2 weeks and above. Fucose staining with UEA-I was first detected in the principal cells in mice aged 3 weeks. Staining of sialic acid with MAL-I was first detected in all undifferentiated epithelial cells in mice aged 1 week, and this characteristic became specific to the narrow and clear cells in all regions and to the principal cells in regions IV and V in mice aged 3 weeks. The results indicate that epididymal differentiation is characterized by the expression of cell- and region-specific sugar chains that appear early during postnatal development before the sperm arrives in the epididymis.     

Epididymis of viscacha (Lagostomus maximus maximus): morphological changes during the annual reproductive cycle

Little is known about morphological changes in the epididymis in relation to the natural photoperiod or their influence on sperm maturation. The viscacha is a seasonal rodent living in the Southern Hemisphere. The adult males exhibit an annual reproductive cycle with periods of maximum gonadal activity and gonadal regression. In this work, we studied seasonal variations in the morphology and cellular population of the epididymis during both periods, and we compared these results with those recorded at the testicular level. Epididymides were removed and studied by light microscopy. Measurements of luminal diameter, epithelial height, thickness of the lamina propria, and relative cellular distribution were performed. Analysis of variance (ANOVA) or nonparametric ANOVA was used to compare the results. Striking quantitative and qualitative changes were observed. Epididymides in periods of gonadal regression showed a significant decrease in luminal diameter and epithelial height in cauda, while the thickness of the lamina propria increased. In the epididymal corpus, the number of clear cells increased, and the cytoplasm of principal cells showed numerous giant vacuoles. During the active period, the number of halo cells increased and the cytoplasm of these cells was filled with dense bodies. In conclusion, the epididymis of the viscacha exhibits important seasonal morphological changes throughout annual reproductive cycle. The epididymal corpus and cauda segments appeared to be the segments most sensitive to seasonal cyclical variations of the external environment. We therefore postulate that the epididymal morphology of the viscacha probably could be regulated by the natural photoperiod.     

The initial segment of the rat epididymis is able to uptake immature germ cells shed by testicular damage

The initial segment of the caput epididymidis, the most proximal part of the rat epididymis, has specific functional characteristics. In the present study, the behavior of the epididymal epithelium from this region was evaluated after the exposure to a massive number of immature germ cells in the luminal fluid. The experimental release of immature germ cells from the seminiferous tubules was performed by injecting anti-microtubule compounds into the rete testis and the lumen of seminiferous tubules. Twenty-four hours after nocodazole or colchicine administration, a massive phagocytosis of immature spermatogenic cells, recognized as acrosin-positive structures, was easily observed in the epithelium of the initial segment of the epididymis assessed by light and electron microscopy. Immature germ cells were engulfed by epithelial cells, where most of them were found as cell debris at different stages of degradation. No signs of inflammation were observed either in the lumen or in the interstitium. The phagocytosis of immature germ cells was restricted to the epithelium of the initial segment of the epididymis, suggesting a role for this segment as the first selective barrier for the exclusion of abnormal gametes along the male genital tract.     

Effects of Estrogen Treatment on Aging in the Rat Epididymis

Previous studies from our laboratory demonstrated that estrogen signaling in the testis contributes to maintaining spermatogenesis in adult rats, and that estrogen treatment attenuated the age-associated decline in sperm production. The purpose of this study was to determine if epididymal function is also altered with age, and what effects estrogen treatment may have on the epididymis during aging. We compared untreated rats at 3 and 15 months of age to 18-month-old vehicle-treated and estrogen treated rats. In all four groups, tubule and lumen diameter of the cauda was significantly larger than more proximal regions of the epididymis. In the 3-, 15-, and 18-month-old treated animals, the epithelial cell height of the cauda was significantly shorter than that of more proximal regions. The caput cell height was shorter at 18 months compared to 3 months but this was not seen in estrogen treated animals. Thus, estrogen appears able to prevent some age related changes in epididymal morphology. Sperm transit time through the distal cauda was significantly delayed with aging. Estrogen treatment prevented this delay, indicating that sperm transit through the epididymis is an estrogen regulated function. Differences in estradiol and testosterone concentrations were observed between 3- and 15-month-old animals, but no further differences were noted between treated or untreated animals at 18 months. Interestingly, expression of androgen receptor and estrogen receptor alpha were similar between ages and treatments. Collectively, these results suggest epididymal morphology and function are affected by aging and estrogen treatment. Anat Rec, 302:1447–1457, 2019. © 2018 Wiley Periodicals, Inc.