The differential absorptive activity of epithelial cells of the rat epididymus before and after castration

Activin and follistatin interactions in the male reproductive tract: activin expression and morphological abnormalities in mice lacking follistatin 288

Activin A is an important regulator of testicular and epididymal development and function, as well as inflammation and immunity. In the adult murine reproductive tract, activin A mRNA (Inhba) expression levels are highest in the caput epididymis and decrease progressively towards the distal vas deferens. The activin-binding protein, follistatin (FST), shows the opposite expression pattern, with exceptionally high levels of the Fst288 mRNA variant in the vas deferens. This unique pattern of expression suggests that activin A and follistatin, in particular FST288, play region-specific roles in regulating the epididymis and vas deferens. The cellular distribution of activin and follistatin and structural organization of the male reproductive tract was examined in wild-type and transgenic (TghFST315) mice lacking FST288. Compared to wild-type littermates, TghFST315 mice showed a 50% reduction in serum follistatin and a significant elevation of both activin A and B. Testicular, epididymal and seminal vesicle weights were reduced, but intra-testicular testosterone was normal. A decrease in the epididymal duct diameter in the corpus and thickening of the peritubular smooth muscle in the cauda, together with increased coiling of the proximal vas deferens, were observed in TghFST315 mice. No immune cell infiltrates were detected. Immunohistochemistry indicated that epithelial cells are the main source of activins and follistatin in the epididymis and vas deferens. Activin A, but not activin B, was also localized to sperm heads in the lumen of the epididymis and vas deferens. Expression of Inhba and another immunoregulatory gene, indoleamine-2,3-dioxygenase (Ido-1), was increased approximately twofold in the TghFST315 caput epididymis, but several other genes associated with immunoregulation, inflammation or fibrosis were unaffected. Our novel data indicate that disruption of follistatin expression has significant effects on the testis and epididymis, and suggest an association between activin A and indoleamine-2,3-dioxygenase in the caput epididymis, with implications for the epididymal immunoenvironment.

Seasonal immunohistochemical reactivity of S-100 and α-smooth muscle actin proteins in the epididymis of dromedary camel, Camelus dromedarius

The S-100 and alpha smooth muscle actin (α-SMA) proteins have been localised in epididymal tissue of several mammalian species, but there have been no data for a seasonal work in camel. The aim of this study was to investigate the immunoreactivities of S-100 and α-SMA proteins in the epididymis of dromedary camel during breeding and nonbreeding seasons. The immunopositive signals for both proteins were observed in different regions of camel epididymis. S-100-immunopositive signals were noted in both the epididymal epithelium and the intertubular connective tissue, while α-SMA signals were confined to the intertubular connective tissue, especially in the peritubular smooth muscle coat and the blood vessels. This study showed an increase in the intensity of S-100 and α-SMA immunoreactions during the breeding season in different regions of camel epididymis than that seen in the nonbreeding season. In conclusion, epididymis might be considered as a source of S-100 and α-SMA proteins in the camel and the secretion of these proteins showed distinct seasonal variations. Further, S-100 and α-SMA may affect the structural and physiological states of the epididymal duct.

Regulation of luminal acidification by the V-ATPase

Specialized cells in the body express high levels of V-ATPase in their plasma membrane and respond to hormonal and nonhormonal cues to regulate extracellular acidification. Mutations in or loss of some V-ATPase subunits cause several disorders, including renal distal tubular acidosis and male infertility. This review focuses on the regulation of V-ATPase-dependent luminal acidification in renal intercalated cells and epididymal clear cells, which are key players in these physiological processes.

Ultrastructure of the epithelium lining of cauda epididymidis in mongrel dogs

The epithelium lining of cauda epididymidis in mongrel dogs was examined by transmission electron microscopy. The epididymal epithelium is pseudostratified with stereocilia and is composed predominantly of principal and clear cells. Therefore, exist basal and apical cells. The principal and clear cells show features suggesting that they may be preferentially involved in absorptive and secretive functions. These results are compared with previously published data on the cauda epididymidis of other mammalian species, in order to understand the significance of the epididymis in sperm maturation.

Comparative morphometric and glycohistochemical studies on the epididymal duct in the donkey (Equus asinus) and dromedary camel (Camelus dromedarius)

The present study was undertaken to compare morphometric and glycohistochemical differences in the epididymal duct of the donkey and the dromedary camel. Paraffin-embedded sections from the different regions of the duct (caput, corpus and cauda) of both species were stained conventionally for general histology and histomorphometry and also with fluorescein isothiocyanate (FITC) conjugated lectins for glycohistochemical mapping. Morphometric data (means ± SE) showed that the luminal diameter was widest (1029.76 ± 15.04 μm) in the donkey cauda and narrowest (179.80 ± 3.27 μm) in the camel corpus. The thickness of the peritubular muscle coat had the highest (74.32 ± 1.85 μm) and the lowest (24.32 ± 0.74 μm) values in the donkey cauda and corpus respectively. The greatest (94.44 ± 2.08 μm) and the least (21.48 ± 0.66 μm) values of epithelial height were reported respectively in the camel caput and in the donkey cauda. The length of stereocilia of principal cells in the camel was greatest (21.88 ± 0.57 μm) and lowest (6.68 ± 0.28 μm) in the caput and cauda. Binding sites for only six out of eight lectins could be found. The distribution pattern of binding sites of different lectins showed significant variations in both a species-specific and also region-specific manner. Distinct labeling was found in the Golgi zone, apical cytoplasm and on stereocilia of principal cells in the camel (WGA and DBA) and donkey (DBA) caput region, while other lectins exhibited variable reactivity in the other regions in both species. The basal cells showed variable binding to most of the lectins, however, they displayed distinct binding to WGA and PSA throughout the duct in camel and donkey respectively. In conclusion, both morphometric and glycohistochemical findings displayed regional species-specific and potentially functional relevant characteristics.

Histological and immunohistochemical studies on the epididymal duct in the dromedary camel (Camelus dromedarius)

This study was conducted to underscore the spatial distribution of some biologically active proteins within the epididymal duct in the dromedary camel. Paraffin-embedded sections from different regions of epididymis were stained by conventional histological techniques and by immunohistochemistry. A battery of primary antibodies against six proteins (S100, alpha smooth muscle actin [α-SMA], connexin-43 [Cx43], galactosyltransferase [GalTase], angiotensin converting enzyme [ACE], and vascular endothelial growth factor [VEGF]) were used. The epididymal epithelium consisted of five cell populations: principal, basal, apical, dark, and halo cells. The histochemical findings indicated the absence of binding sites for VEGF and Cx43. The principal cells (PCs) showed variable immunoreactivity (IR) for ACE, S100, and GalTase throughout the whole length of the duct. The apical surfaces of most PCs (at the caput) and some PCs (at the corpus) exhibited intense ACE-IR, whereas those at the cauda displayed alternating negative and strong immunostaining. Similarly, moderate S100-IR was found in cytoplasm and nuclei of all PCs at the caput, few PCs at the corpus, and several PCs alternating with negative PCs at the cauda. In contrast, only some PCs showed weak to strong GalTase-IR in different regions. Apart from negative to weak positive S100-IR, basal cells failed to show IR for all other proteins. Apical cells displayed strong IR for ACE, S100, and GalTase with some regional differences. The peritubular and vascular smooth muscle cells revealed strong α-SMA-IR in all regions. In conclusion, the spatial distribution of different proteins in camel epididymis showed similarities and differences to other mammalian species. The region-specific topographic distribution of different proteins and cell types might indicate that the caput and cauda are metabolically more active than that of the corpus.

Establishment of cell-cell cross talk in the epididymis: control of luminal acidification

Male infertility is often caused by sperm that have low motility and interact poorly with the oocyte. Spermatozoa acquire these crucial functions in the epididymis. A low luminal bicarbonate (HCO(3)(-)) concentration and low pH keep sperm quiescent during their maturation and storage in this organ. This review describes how epididymal epithelial cells work in a concerted manner, together with spermatozoa, to establish and maintain this acidic luminal environment. Clear cells express the proton-pumping ATPase (V-ATPase) in their apical membrane and actively secrete protons. HCO(3)(-) induces V-ATPase accumulation in apical microvilli in clear cells via HCO(3)(-)-sensitive adenylyl cyclase-dependent cAMP production. HCO(3)(-) is secreted from principal cells following basolateral stimulation, to transiently "prime" spermatozoa before ejaculation. Luminal ATP and adenosine also induce V-ATPase apical accumulation in clear cells via activation of P2 and P1 receptors, respectively. ATP is released into the lumen from sperm and principal cells and is then metabolized into adenosine by local nucleotidases. In addition, the V-ATPase is regulated by luminal angiotensin II via activation of basal cells, which can extend narrow body projections that cross the tight junction barrier. Basal cells then secrete nitric oxide, which diffuses out to stimulate proton secretion in clear cells via activation of the cGMP pathway. Thus, an elaborate communication network is present between principal cells and clear cells, and between basal cells and clear cells, to control luminal acidification. Monitoring and decoding these "intercellular conversations" will help define pathophysiologic mechanisms underlying male infertility.

Proteomic analysis of V-ATPase-rich cells harvested from the kidney and epididymis by fluorescence-activated cell sorting

Proton-transporting cells are located in several tissues where they acidify the extracellular environment. These cells express the vacuolar H(+)-ATPase (V-ATPase) B1 subunit (ATP6V1B1) in their plasma membrane. We provide here a comprehensive catalog of the proteins that are expressed in these cells, after their isolation by enzymatic digestion and fluorescence-activated cell sorting (FACS) from transgenic B1-enhanced green fluorescent protein (EGFP) mice. In these mice, type A and B intercalated cells and connecting segment cells of the kidney, and narrow and clear cells of the epididymis, which all express ATP6V1B1, also express EGFP, while all other cell types are negative. The proteome of renal and epididymal EGFP-positive (EGFP(+)) cells was identified by liquid chromatography-tandem mass spectrometry (LC-MS/MS) and compared with their respective EGFP-negative (EGFP(-)) cell populations. A total of 2,297 and 1,564 proteins were detected in EGFP(+) cells from the kidney and epididymis, respectively. Out of these proteins, 202 and 178 were enriched by a factor greater than 1.5 in EGFP(+) cells compared with EGFP(-) cells, in the kidney and epididymis respectively, and included subunits of the V-ATPase (B1, a4, and A). In addition, several proteins involved in intracellular trafficking, signaling, and cytoskeletal dynamics were identified. A novel common protein that was enriched in renal and epididymal EGFP(+) cells is the progesterone receptor, which might be a potential candidate for the regulation of V-ATPase-dependent proton transport. These proteomic databases provide a framework for comprehensive future analysis of the common and distinct functions of V-ATPase-B1-expressing cells in the kidney and epididymis.

Epididymal hypo-osmolality induces abnormal sperm morphology and function in the estrogen receptor alpha knockout mouse

Estrogen receptor-alpha (ESR1) is highly expressed in the efferent ductules of all species studied as well as in the epididymal epithelium in mice and other select species. Male mice lacking ESR1 (Esr1KO) are infertile, but transplantation studies demonstrated that Esr1KO germ cells are capable of fertilization when placed in a wild-type reproductive tract. These results suggest that extratesticular regions, such as the efferent ductules and epididymis, are the major source of pathological changes in Esr1KO males. Previous studies have shown alterations in ion and fluid transporters in the efferent duct and epididymal epithelia of Esr1KO males, leading to misregulation of luminal fluid pH. To determine the effect of an altered epididymal milieu on Esr1KO sperm, we assayed sperm morphology in the different regions of the epididymis. Sperm recovered from the epididymis exhibited abnormal flagellar coiling and increased incidence of spontaneous acrosome reactions, both of which are consistent with exposure to abnormal epididymal fluid. Analysis of the epididymal fluid revealed that the osmolality of the Esr1KO fluid was reduced relative to wild type, consistent with prior reports of inappropriate fluid absorption from the efferent ductules. This, along with the finding that morphological defects increased with transit through the epididymal duct, suggests that the anomalies in sperm are a consequence of the abnormal luminal environment. Consistent with this, incubating Esr1KO sperm in a more wild-type-like osmotic environment significantly rescued the abnormal flagellar coiling. This work demonstrates that Esr1KO mice exhibit an abnormal fluid environment in the lumen of the efferent ducts and epididymis, precluding normal sperm maturation and instead resulting in progressive deterioration of sperm that contributes to infertility.

LXR and ABCA1 control cholesterol homeostasis in the proximal mouse epididymis in a cell-specific manner

Mammalian spermatozoa undergo important plasma membrane maturation steps during epididymal transit. Among these, changes in lipids and cholesterol are of particular interest as they are necessary for fertilization. However, molecular mechanisms regulating these transformations inside the epididymis are still poorly understood. Liver X receptors (LXRs), the nuclear receptors for oxysterols, are of major importance in intracellular cholesterol homeostasis, and LXR(-/-)-deficient male mice have already been shown to have reduced fertility at an age of 5 months and complete sterility for 9-month-old animals. This sterility phenotype is associated with testes and caput epididymides epithelial defects. The research presented here was aimed at investigating how LXRs act in the male caput epididymidis by analyzing key actors in cholesterol homeostasis. We show that accumulation of cholesteryl esters in LXR(-/-) male mice is associated with a specific loss of ABCA1 and an increase in apoptosis of apical cells of the proximal caput epididymidis. ATP-binding cassette G1 (ABCG1) and scavenger receptor B1 (SR-B1), two other cholesterol transporters, show little if any modifications. Our study also revealed that SR-B1 appears to have a peculiar expression pattern along the epididymal duct. These results should help in understanding the functional roles of LXR in cholesterol trafficking processes in caput epididymidis.

Effect of deprivation of endogenous follicle stimulating hormone on rat epididymis: a histological evaluation

The growth and function of the epididymis are regulated by testosterone produced by Leydig cells in the testes. In the present study it was observed that neutralization of endogenous follicle stimulating hormone (FSH) in immature rats using a highly specific antiserum to ovine FSH resulted in changes in the histology of the epididymis along with a decrease (50-60%) in its weight compared with the normal serum-treated controls. These changes were observed in both rat and monkey epididymis without any decrease in serum testosterone, on which epididymis is known to be dependent. A detailed study was therefore carried out on the effects of deprivation of FSH or testosterone on the histology of epididymis. The changes in epididymal histology following FSH deprivation included a decrease in the size of the tubule lumen in the rat as well as in the adult male bonnet monkey in which the antiserum against ovine FSH was raised. Intensive vacuolization and uneven surface of the luminal epithelium was also observed. In contrast, the effect of deprivation of testosterone support by way of administration of LH antiserum or fiutamide resulted in a decrease in the size of the lumen and degenerative changes. These results suggest that cauda epididymidis is a target for FSH action.

Androgenic regulation of novel genes in the epididymis

The epididymis is critically dependent on the presence of the testis. Although several hormones, such as retinoids and progestins, and factors secreted directly into the epididymal lumen, such as androgen binding protein and fibroblast growth factor, might play regulatory roles in epididymal function, testosterone (T) and its metabolites, dihydrotestosterone (DHT) and estradiol (E2), are accepted as the primary regulators of epididymal structure and functions, with the former playing the greater role. To ascertain the molecular action of androgens on the epididymis, three complementary approaches were pursued to monitor changes in gene expression in response to different hormonal milieux. The first was to establish changes in gene expression along the epididymis as androgenic support is withdrawn. The second was to determine the sequence of responses that occur in an androgen deprived tissue upon re-administration of the two metabolites of T, DHT and E2. The third was to study the effects of androgen withdrawal and re-administration on gene expression in immortalized murine caput epididymidal principal cells. Specific responses were observed under each of these conditions, with an expected major difference in the panoply of genes expressed upon hormone withdrawal and re-administration; however, some key common features were the common roles of genes in insulin like growth factor/epidermal growth factor and the relatively minor and specific effects of E2 as compared to DHT. Together, these results provide novel insights into the mechanisms of androgen regulation in epididymal principal cells.

Role of acid/base transporters in the male reproductive tract and potential consequences of their malfunction

Acid/base transporters play a key role in establishing an acidic luminal environment for sperm maturation and storage in the male reproductive tract. Impairment of the acidification capacity of the epididymis, via either genetic mutations or exposure to environmental factors, may have profound consequences on male fertility.

Effects of streptozotocin-diabetes and insulin replacement on the epididymis of prepubertal rats: histological and histomorphometric studies

The present study evaluates the effects of streptozotocin (STZ)-induced diabetes and insulin replacement on the histoarchitecture of caput, corpus, and caudal epididymides during the critical period of sexual maturation in rats. Prepubertal male Wistar rats (40 days old) were made diabetic by a single injection of STZ (120 mg/kg body weight, intraperitoneally). To one set of diabetic rats, insulin was replaced daily at a dose of 3 U/100g body weight, subcutaneously in two equally divided doses at 8:00 a.m. and 6:00 p.m. All the rats were killed on the 61st day of postnatal life. STZ-diabetes reduced the body weight and also caused regression of epididymis, leading to a decrease in the absolute weight of caput, corpus, and caudal regions. Histological studies also revealed a considerable reduction in the size of the tubule and lumen of these segments with an increase in interstitial stroma. Because of shrinkage of tubules, principal cells were packed tightly with clumping of nuclei. Stereological studies support atrophic changes in the caput, corpus, and caudal epididymides by reduction in tubular diameter, volume, and surface density. The epididymal lumen of STZ-treated rats was totally devoid of spermatozoa. These findings emphasize the detrimental effects of diabetes on the maintenance and establishment of fully differentiated epididymal epithelium during sexual maturation. Insulin replacement was only able to prevent the adverse effects of diabetes on certain parameters and this response was region-specific.

Postnatal development and regulation of beta-hexosaminidase in epithelial cells of the rat epididymis

beta-Hexosaminidase (Hex) catalyzes the hydrolysis of terminal sugar residues from a number of substrates such as GM2 gangliosides, glycoproteins, glycolipids, and glycosaminoglycans. As an enzyme present in lysosomes of epithelial cells of the adult rat epididymis, it serves to degrade substances endocytosed from the epididymal lumen. In this way, it modifies and creates a luminal environment where sperm can undergo their maturational modifications. In this study, the postnatal developmental pattern of expression of Hex was examined in animals from days 7-56. In addition, the role of testicular factors on Hex expression in the different cell types and regions of the epididymis of adult rats was examined in orchidectomized and efferent duct-ligated rats. Both parameters were examined on Bouin-fixed epididymides in conjunction with light microscope immunocytochemistry. At postnatal day 7, the epithelium of the entire epididymis was unreactive for anti-Hex antibody. By day 21, narrow and clear cells of their respective regions became reactive, whereas basal cells became reactive only by day 29. Principal cells displayed only an occasional reactive lysosome at day 21, several by day 29, and numerous reactive lysosomes by day 39, comparable to the region-specific distribution noted for 90-day-old animals, and at an age when high androgen levels are attained. Thus, postnatal onset of Hex expression varies according to the different cell types of the epididymis, suggesting different regulatory factors. This finding was confirmed from studies employing adult orchidectomized and efferent duct-ligated adult rats. Indeed, in all experimental animals, Hex immunostaining in narrow, clear, and basal cells was intense and comparable to control animals. In contrast, there was a notable absence of lysosomal staining in principal cells at all time points after orchidectomy, which was restored, however, following testosterone replacement. No effect on Hex expression was observed in efferent duct-ligated animals. Taken together, the data suggest that Hex expression in lysosomes of principal cells is regulated by testosterone or one of its metabolites. However, the expression of Hex being independent of testicular factors in narrow, clear, and basal cells of adult animals, but occurring at different time points during postnatal development, suggests that different regulatory factors are responsible for onset of Hex expression in these cell types during development.

Regulation of sulfated glycoprotein-1 and cathepsin D expression in adult rat epididymis

Endocytosis, whereby proteins are internalized from the epididymal lumen to be eventually degraded in lysosomes, is one of the major functions of the epididymal epithelial cells in maintaining a proper luminal milieu conducive for sperm maturation. In the present study, using light microscope immunocytochemical methods, we examined the regulation of 2 lysosomal enzymes, sulfated glycoprotein-1 (SGP-1) and cathepsin D, in adult rat epididymides fixed in Bouin fixative and embedded in paraffin. After orchidectomy (O) with or without testosterone (T) supplementation, efferent duct ligation (EDL), or hypophysectomy (H), lysosomes of principal cells were intensely reactive with the anti-SGP-1 antibody, as were narrow, clear, and basal cells, with staining patterns similar to that of control animals. These experimental procedures also had no effect on cathepsin D expression in all cell types, except for clear cells of the corpus and cauda epididymidis, which after orchiedectomy and hypophysectomy, became intensely reactive, unlike their completely unreactive state in control animals. In O+T animals, as well as in EDL animals, clear cells remained unreactive. These data taken together suggest that expression of SGP-1 is not under the control of testicular or pituitary factors, as is also the case for cathepsin D expression by principal, narrow, and basal cells. However, specific inhibition of cathepsin D expression by testosterone or one of its metabolites appears to occur in clear cells of the corpus and cauda epididymidis. Furthermore, in addition to small, typical lysosomes, principal cells also revealed large supranuclear and infranuclear spherical structures that were immunoreactive with both anti-SGP-1 and anti-cathepsin D antibodies, suggesting their lysosomal nature. With electron microscopy, these structures appeared electron-lucent and contained membranous profiles embedded in an electron-dense, granular background. Such images suggest that the various experimental procedures adversely affect the expression of several other lysosomal enzymes in principal cells, leading to a lysosomal phenotype similar to that observed in various lysosomal storage diseases.

Epididymal epithelial cell involution following a single intraperitoneal administration of ethane dimethanesulfonate in the goat (Capra hircus)

Ethane dimethanesulfonate (EDS) selectively destroys Leydig cells in rats and a few other smaller animal species but not in mice and quail. In the teleost fish, it stimulates testicular activity instead. It also causes formation of sperm granulomas, reduction of sperm fertilizing ability, and destruction of clear cells in the epididymis. Investigations involving larger animal species are scanty. We have previously reported that EDS has no effect on goat Leydig cells but appears to have a direct cytotoxic effect on the seminiferous epithelium. This study was therefore designed to investigate the effects of EDS on goat epididymal cytoarchitecture. EDS was administered intraperitoneally at two dose levels, 75 and 25 mg/kg body wt. The former dose was rather toxic, killing three of five goats in this group within 24 h whereas the latter dose was well tolerated. Six days after treatment, the goats were hemicastrated and the epididymis was isolated and processed for light and electron microscopy. Involution associated with EDS was observed in epithelial cells of all regions of the epididymis, each having its own specific and peculiar changes. In the caput, there was increased cytoplasmic density accompanied by enlarged vacuoles and paucity of secretory vesicles in the apical cytoplasm. The Golgi cisternae were dilated and disorganized and, in the basal aspect, large dense staining bodies or inclusions, degenerative mitochondria, and lamellated bodies were observed. In the corpus, large vacuoles containing flocculent materials occurred in the entire cell cytoplasm but were particularly numerous and large in the midcytoplasm, completely obliterating the Golgi area. There was a dramatic reduction in epithelial height in the cauda epididymis accompanied by sparse distribution of markedly shortened microvilli. The epithelial cells had extensively lobulated nuclei and disorganized cytoplasm with dilated Golgi apparatus and large conglomerations of tubular structures. These structural changes suggest that EDS causes degeneration of goat epididymal epithelial cells. These effects are likely to result from the direct action of the compound on the epithelium.

Expression and regulation of H+K+ATPase in lysosomes of epithelial cells of the adult rat epididymis

Endocytosis is an important event in the epididymis as it contributes to a luminal environment conducive for sperm maturation. Principal and clear cells contain numerous lysosomes which degrade many substances internalized by endocytosis from the epididymal lumen. The interior of the lysosomes depends on low pH to activate the release of their enzymes and to activate their acid hydrolases. In the present study, H+K+ATPase was localized by light microscopy in the adult rat epididymis of intact and of orchidectomized animals supplemented with testosterone or not. In normal animals, numerous lysosomes of nonciliated cells of the efferent ducts were intensely reactive for anti-H+K+ATPase antibody. In the initial segment, only a few lysosomes of principal cells were reactive. In the intermediate zone of the epididymis, numerous lysosomes of principal cells were intensely reactive, while the number of intensely reactive lysosomes decreased progressively from the proximal caput to the distal caput with none being seen in the proximal corpus region. In the distal corpus and cauda regions, only a few lysosomes of some principal cells were reactive. In contrast, clear cells of all regions showed intense reactivity. Orchidectomy resulted in the abolishion of H+K+ATPase in lysosomes of principal cells of all regions except the initial segment. However, while clear cells of the caput and corpus regions also became unreactive, those of the cauda region remained as reactive as in controls. Orchidectomized animals supplemented with testosterone maintained a staining pattern similar to controls for both cell types. These observations demonstrate the presence in principal and clear cells of H+K+ ATPase which may have an important role in acidifying the interior of their lysosomes. However, there is a region-specific expression of H+K+ATPase in lysosomes of principal cells, unlike that for clear cells. In addition, H+K+ATPase expression in lysosomes of principal cells depends on testosterone in all regions except the initial segment. However, in the case of clear cells, only those of the caput and the corpus regions are dependent on testosterone, while those of the cauda region appear to be regulated by some other factor.

Cathepsin A is expressed in a cell- and region-specific manner in the testis and epididymis and is not regulated by testicular or pituitary factors

The epithelial cells of the testis are involved in the production, differentiation, and sustenance of sperm, and those of the epididymis play a major role in sperm maturation, protection, and storage. These tissues express various proteins that respond differently to androgens. Cathepsin A is a multifunctional lysosomal carboxypeptidase that also functions as a protective and an activator protein for neuraminidase and beta-galactosidase. In this study, cathepsin A was immunolocalized by light and electron microscopy using a polyclonal affinity-purified antibody on the testis and epididymis of normal, orchidectomized with or without testosterone supplementation, efferent duct-ligated, and hypophysectomized adult rats. In normal rats, cathepsin A expression was noted in lysosomes of Sertoli and Leydig cells but not in germ cells of the testis, as well as nonciliated cells of the efferent ducts. In the epididymis, a cell- and region-specific distribution of cathepsin A was noted. In experimentally treated animals, no changes were noted in the expression of cathepsin A. Immunolabeling of tissues examined at the electron microscopic level revealed that lysosomes were reactive. These data indicate cell- and region-specific expression of cathepsin A in cells of the testis and epididymis and also indicate that cathepsin A expression is not regulated by testicular or pituitary factors.

Expression and regulation of LRP-2/megalin in epithelial cells lining the efferent ducts and epididymis during postnatal development

Low density lipoprotein receptor-related protein-2/megalin (LRP-2) is a receptor belonging to the low density lipoprotein receptor family that mediates endocytosis and lysosomal degradation of a variety of ligands including apolipoprotein J (Apo J)/clusterin/SGP-2. LRP-2 has been shown to be expressed regionally in the adult rat epididymis. In this study, we describe the pattern of expression of LRP-2 in the efferent ducts and epididymis during postnatal development of the rat and examine the role of testicular luminally derived substances on its expression. The expression of LRP-2 was analyzed immunocytochemically in tissues of normal animals ranging in age from postnatal day 7-90 and in 15-day-old efferent-duct-ligated animals sacrificed at later ages. In the efferent ducts, LRP-2 expression, appearing as a dense band on the apical surface of the nonciliated epithelial cells, was noted as early as day 7, well before the entry of sperm, Sertoli-cell-derived secretory products, and high levels of androgens. Efferent duct ligation studies further revealed that expression under this condition was comparable to controls at all later ages examined, suggesting that the factor regulating its expression was not a luminally derived testicular substance. In normal untreated animals, LRP-2 expression was not apparent at any of the ages examined in the proximal initial segment of the epididymis. By comparison, the distal initial segment, although having no LRP-2 expression from 7-15 days, showed expression in principal cells by day 21 which intensified at days 29 and 39. However, by day 49 and at later ages (56 and 90), LRP-2 immunoreactivity over principal cells became spotty or with weak or moderate reactivity in some cells and none in others. LRP-2 expression in the intermediate zone, proximal caput, corpus, and cauda regions also appeared in principal cells by day 21, intensified at days 29 and 39 and persisted as such at all later ages examined, correlating with high levels of androgens shown to occur by day 39. Although LRP-2 expression in the distal caput region was evident in principal cells at days 21 and 29, it became spotty with weak, moderate, or absent reactivity over principal cells at all later ages. These data suggest that LRP-2 expression is under the influence of both stimulatory and region-specific inhibitory factors. Analysis of 15-day-old efferent-duct-ligated animals at all later ages examined revealed that there was no change in LRP-2 expression along the entire epididymis, suggesting that both the stimulatory and inhibitory factors are not luminally derived testicular substances. The observed pattern of LRP-2 expression in all regions of the epididymis, except the distal caput region, was similar to that described for Apo J internalization by principal cells during postnatal development, showing a correlation between LRP-2 expression and its ligand, Apo J. In summary, LRP-2 expression in the epididymis undergoes region-specific changes during postnatal development and appears to be influenced by both stimulatory and inhibitory factors.

Morphological and histochemical changes in the epididymis of hamsters (Mesocricetus auratus) subjected to short photoperiod

The morphological involution and histochemical changes of the Syrian hamster (Mesocricetus auratus) epididymis induced by a short light period were investigated. Under short-day conditions, the epididymis showed marked morphological changes including a decrease in luminal diameter, disappearance of spermatozoa, increase of interductal tissue, increase of intraepithelial lipofuscin deposits, the presence of phagolysosomes in the principal cells and macrophage-like cells, and a considerable modification of most clear cells. With lectin histochemistry changes were found in the glycoconjugates of principal cells of the regressed epididymis, either a decrease (PNA, WGA, HPA and DBA) or an increase (MAA) in the affinity of lectins to the Golgi area, or a decrease (HPA) or an increase (PNA) in lectin binding to stereocilia. Both morphological and histochemical results showed that, under this light condition, the cauda epididymidis presented the most prominent alterations, and that the epididymis showed increased absorptive activity and a decreased synthesis of glycoproteins. All these changes are probably due to the decrease in testosterone levels.

Structural features and functions of principal cells of the intermediate zone of the epididymis of adult rats

BACKGROUND

In the present study, principal cells of the intermediate zone of the epididymis, an area situated between the initial segment and proximal caput, were observed to present morphological features distinct from those of principal cells of other regions.

METHODS

The epididymides of adult rats were fixed by perfusion with glutaraldehyde and embedded in Epon. Administration of fluid phase tracers was performed in the case of several animals. Localization of anti-SGP-2 and anti-immobilin antibodies in conjunction with light (LM) and electron (EM) microscope immunocytochemistry was also performed.

RESULTS

In the LM and EM, the most distinctive feature of many principal cells of this zone was the presence of apically located vacuoles referred to as giant endosomes due to their large size and because they readily incorporated tracers introduced into the lumen of the epididymal duct and were acid phosphatase-negative. Giant endosomes, containing electron-dense granular patches, appeared to form by the progressive fusion of small, medium, and large endosomes. In the supranuclear region, multivesicular bodies (MVBs) and lysosomes were present. Although smaller in size than the giant endosomes, MVBs and lysosomes contained the electron-dense patches. It is suggested from morphological images that giant endosomes fragment into smaller units corresponding to MVBs which gradually transform into lysosomes. Experiments using anti-SGP-2 and anti-immobilin antibodies revealed gold particles over the Golgi apparatus and secretory vesicles (150-300 nm) of principal cells of this zone as well as the luminal contents indicative of secretion of these proteins. Interestingly, giant endosomes were also immunolabeled with both antibodies as were stereocilia, coated pits and vesicles, and endosomes of various sizes; lysosomes were minimally labeled. These results suggest that principal cells of the intermediate zone endocytose as well as secrete SGP-2 and immobilin. The internalized SGP-2 and immobilin may correspond to that secreted further upstream and that, possibly due to their short half-life and terminated function, are removed from the lumen of the duct. Principal cells of this zone secrete these proteins possibly to replenish that lost by endocytosis.

CONCLUSIONS

Principal cells of the intermediate zone contain giant endosomes. The presence of such large structures suggests that the early events in endocytosis is a slower process in principal cells of this zone as compared to other regions. The fact that these cells both secrete and endocytose SGP-2 and immobilin adds to the complexity of our understanding of how principal cells function along the length of the epididymis.

The apical mitochondria-rich cells of the mammalian epididymis

The morphology and function of the apical mitochondria-rich cells in the mammalian ductus epididymidis epithelium are revised. These cells are similar in all mammalian species studied. Apical mitochondria-rich cells are scarce (1-5 cells/100 principal cells) and are mainly found in the initial epididymal segments. Their morphology varies from slender cells that extend from the basal lamina to the epididymal lumen, to round cells that protrude into the lumen and are not in contact with the basal lamina. Their cytoplasm is more electron-dense than that of principal cells and contains more mitochondria which, in some species, are surrounded by rough endoplasmic reticulum cisternae. The adluminal cytoplasm displays a few short microvilli and contains many acid phosphatase positive vesicles. Apical mitochondria-rich cells differ from the principal cells in some histochemical features such as: (a) different lectin-staining pattern; (b) more intense reaction to the enzymatic activities: carbonic anhydrase, Ca(2+)-ATPase, peanut-agglutinin-sialidase, NADP dehydrogenase, succinate dehydrogenase, alpha-galactosidase and beta-galactosidase; (c) more intense immunoreaction to several cytokeratin types and to estradiol-related receptor protein; (d) weaker immunoreaction to epithelial membrane antigen and to retinol-binding protein. Although the function of the apical mitochondria-rich cells is still unknown, the following possible functions have been suggested: holocrine secretion; cooperation with the principal cells in epididymal reabsorption of testicular fluid; and acidification of epididymal fluid. Experimental results suggest that differentiation and maintenance of apical mitochondria-rich cells are not under androgen control and that these cells are sensitive to estrogen stimulation.

Effects of vasectomy on the epididymis

Common principles can be discerned in the response of the epididymis to vasectomy, despite species differences. Increases in the size and number of lysosomes are the most frequent changes in the epididymal epithelium. The presence or absence of additional alterations such as changes in the height of the epithelium may be related to variations in distensibility of the vas deferens and epididymis. Direct measurements by micropuncture of epididymal and seminiferous tubule hydrostatic pressure indicate that, contrary to dogma, increased pressure in the distal epididymis after vasectomy is not generally transmitted to the seminiferous tubules. The epididymal interstitium shows microscopic changes indicative of chronic inflammation, with infiltration of macrophages, lymphocytes, and plasma cells, and rats with these lesions have higher antisperm antibody levels than animals lacking epididymal changes. Macrophages and neutrophils may enter the duct through the epididymal epithelium, at sites of rupture of the duct, and in the efferent ductules. Cyst-like spermatic granulomas occur in virtually all species where the epididymis or vas deferens ruptures with escape of spermatozoa. The sites and timing of granuloma formation may depend on the mechanical properties of the tract in different species, and they are probably important in the immune response to vasectomy. Postvasectomy sera in Lewis rats recognize a consensus repertoire of dominant autoantigens that closely resembles the antigens bound by sera from rats immunized with isologous spermatozoa. There are multiple routes for disposal of the sperm that continue to be produced after vasectomy.

Developmental expression of immobilin in the rat epididymis

BACKGROUND

Immobilin is a protein secreted by principal cells of the distal initial segment, intermediate zone and caput epididymidis of adult rats, which serves to immobilize spermatozoa. In the distal cauda, epithelial clear cells are involved in its endocytosis. The objective of this study was to correlate the developmental events in the maturation of the epididymis with the timing of immobilin secretion and endocytosis in order to evaluate the testicular or epididymal factors which may influence or regulate immobilin expression.

METHODS

Our approach was to follow and compare the developmental expression of immobilin by light microscope immunocytochemistry in control and efferent duct ligated rats of different postnatal ages.

RESULTS

Coincident with the morphological maturation of the principal cells by postnatal day 39, immobilin displayed the characteristic secretory immunostaining pattern found in adults. This adult-like expression occurred despite the absence of spermatozoa in the lumen but was coincident with high levels of circulating and luminal androgens. In contrast, immobilin secretion in rats whose efferent ducts were ligated at day 15 was weak to non-existent in the principal cells of the caput epididymidis at day 28 and remained so into adulthood, indicating that principal cells of this region of the epididymis are dependent either directly or indirectly upon testicular factors present in the lumen for immobilin expression. However, secretion of immobilin in the principal cells of the distal initial segment was unaffected by ligation and unlike the case in control rats high levels of immobilin also continued to be secreted into adulthood by the principal cells of the proximal initial segment. Thus in the distal initial segment immobilin secretion is not regulated by luminal factors originating from the testis, while in the proximal initial segment the normal suppression of immobilin that occurs by postnatal day 39 is. Despite ligation, endocytosis of immobilin by clear cells of the distal cauda epididymidis occurred by day 49, indicating that luminal testicular factors are not essential for stimulating the uptake of immobilin by these cells.

CONCLUSIONS

The results taken together suggest that there are stimulatory and inhibitory luminal testicular factors involved in the regional development of immobilin secretion in the epididymis. There are also immobilin secreting regions in the epididymis, whose secretory development is independent of luminal testicular factors.

Activities and androgenic regulation of kreb cycle enzymes in the epididymis and vas deferens of rhesus monkey

The activities of nine enzymes of the TCA cycle were estimated in the initial segment, caput, corpus and cauda segments of epididymis and vas deferens of adult rhesus monkey and expressed as units per mg DNA. These enzymes were also estimated in epididymal segments and vas deferens of castrated and castrated-androgen replaced monkeys as well. Results indicated higher activities of most of the enzymes in vas deferens as compared to epididymal segments. All the enzymes showed marked reduction in epididymis and vas deferens after castration, the effect being much more pronounced in the epididymis, than in the vas. Androgen replacement in castrated monkeys stimulated most of the enzymes markedly in epididymis and in the vas deferens as compared to their castrated values. The response of cauda and vas deferens to exogenous androgen treatment was however moderate, as compared to the other epididymal segments. The studies indicate that energy metabolism in the epididymis (as well as in the vas deferens) is strictly androgen dependent and the energy charge of these target organs is likely to fall appreciably after castration, which may in turn affect many energy dependent processes of these organs (e.g. absorption, secretion of specific substances etc.) which have been considered important for sperm maturation and survival.

Protein gene product 9.5 and ubiquitin immunoreactivities in rat epididymis epithelium

A quantitative immunohistochemical study was performed of the distribution of protein gene product 9.5 (PGP, a soluble protein localized in neurons and neuroendocrine cells as well as in some non-nervous cells) and ubiquitin along the rat epididymis. In the ductuli efferents, PGP immunoreaction was observed in the whole cytoplasm of some columnar cells; a smaller number of columnar cells showed ubiquitin immunoreactivity with limited apical and basal cytoplasmic localization. In the proximal caput epididymidis, the whole cytoplasm of all columnar cells showed PGP immunoreactivity, ubiquitin immunostaining was negative in this region. In the middle and distal caput epididymidis and the distal cauda, the apical cytoplasm of some columnar cells and the whole cytoplasm of some basal cells showed immunoreactivity to PGP. In these regions, immunoreactivity to ubiquitin was positive in the supranuclear cytoplasm of some columnar cells but not in the basal cells. No immunoreactivity to PGP or ubiquitin was detected in the corpus epididymis and the proximal cauda. Double immunostaining revealed that all the epididymal ubiquitin immunoreactive cells were also PGP immunoreactive, whereas most PGP immunoreactive cells did not immunoreact to ubiquitin. In ubiquitin-PGP immunoreactive cells, the site of the PGP immunoreaction differed from that of the ubiquitin immunoreaction. PGP-ubiquitin immunoreactive cells also seemed to be immunoreactive to anti-AE1/AE3 keratin antibodies. The spermatozoal heads were immunoreactive to PGP antibodies in the epididymal regions from proximal caput to distal cauda but not in the ductuli efferents. The findings suggest that non-ubiquitinated PGP immunoreactive proteins are secreted in the epididymis, mainly in the proximal caput, and attach to spermatozoa.

Ultrastructure of epididymal epithelium in Equus caballus

The ultrastructure of the epithelial lining of the ductuli efferents and the ductus epididymis in the horse (Equus caballus) is described. Several types of cells can be distinguished: ciliated and non-ciliated cells make up the epithelium of the ductuli efferents, whereas principal, apical and basal cells are found in the ductus epididymis. The observations are compared with those made in other species, in particular in the donkey (Equus asinus), and the possible functional roles of the different cell types are discussed.

Regulation of the epididymal glutathione peroxidase-like protein in the mouse: dependence upon androgens and testicular factors

The protein MEP24 was previously described as a glutathione peroxidase-like molecule specifically secreted by the mouse caput epididymidis. Recently, its binding to the head of spermatozoa was demonstrated. Here, the regulation of MEP24 expression was studied by analyzing transcriptional and translational activities in the epididymis (1) of adult mice castrated on day 60 and given various substitutive testosterone (T) treatments from day 90 and (2) of hemicastrated adult animals. In castrated mice, T treatment induced a significant rise in plasma T and 5 alpha-dihydrotestosterone (DHT) concentrations that greatly exceeded the control values. Owing to efficient regulation, however, the epididymal T and DHT levels were never higher than those of the controls. The restoration of MEP24 mRNA accumulation was complete when the epididymal DHT content returned to its normal value. However, when estimated in a cell-free system, the in vitro translatable MEP24 mRNA level never exceeded 70% of control values, even though the DHT and accumulated mRNAs were restored by 100% or more. In hemicastrates, the T content was normal on the castrated side, while the DHT content exhibited a significant decrease (47%). In this case, the MEP24 mRNA accumulation reached 88% of the normal value, but the translation rate, both in vitro and in vivo, was only about 50%. Ultrastructural studies showed that the normal rough endoplasmic reticulum organization in segment I cells is dependent upon the presence of testicular fluid in the epididymal duct lumen. Thus, this report shows that the MEP24 mRNA steady-state level is completely recovered in the presence of a normal epididymal DHT content, while restoration of the regulation of translation is just partial. This could be related to the cell organization but seems mainly dependent upon the presence of specific mRNA-associated factors which are probably under the control of androgens and/or molecules carried by the testicular fluid.

Structural differentiation of the epithelial cells of the testicular excurrent duct system of rats during postnatal development

The light and electron microscopic appearance of the various epithelial cells lining the efferent ducts and different regions of the epididymis were examined in rats on postnatal days 21, 39, 49, 56, and 90 to determine the role of androgens and/or spermatozoa, as well as other possible factors, on the structural differentiation of these cells. Five conclusions may be drawn from the observations made. First, on day 21 epithelial cells of all regions are structurally undifferentiated. Second, it was not until day 49 that nonciliated cells of the efferent ducts resembled those of adult animals, suggesting that more than one factor, such as androgens, testicular products, and/or spermatozoa, is needed for their full structural differentiation. Third, principal cells of the epididymis become structurally differentiated by day 39, i.e., these cells contained an elaborate Golgi apparatus, endoplasmic reticulum cisternae, and numerous 200-400 nm electron lucent secretory vesicles, as well as a full complement of endocytic organelles; this occurred in spite of the absence of spermatozoa in the epididymal lumen. The differentiation of these epididymal cells may be under the influence of androgens, which are known to be high at this time, but may also be due to specific secretions from Sertoli cells secreted directly into the efferent ducts. Fourth, clear cells of the cauda epididymidis are fully differentiated by day 39. The presence of degenerating germ cells in the lumen of the cauda epididymidis and various cellular debris, as well as high androgen levels, may be factors causing the differentiation of the cells of this region. Finally, clear cells of the corpus and cauda epididymidis only become fully differentiated by day 49, at a time when spermatozoa appear in the lumen, despite high levels of androgens at day 39; this observation indicates that the presence of spermatozoa in the lumen may be a necessary factor in causing their differentiation. Overall, these results suggest that a combination of different factors are necessary for the structural differentiation of the various epithelial cell types of the different regions of the epididymis.

Apical mitochondria-rich cells in the human epididymis: an ultrastructural, enzymohistochemical, and immunohistochemical study

An ultrastructural, enzymohistochemical, and immunohistochemical study of the ductus epididymis in normal men was undertaken to investigate the characteristics of the apical mitochondria-rich cells (AMRCs). These cells, which differ morphologically from the principal cells (PCs), appear in isolation in the caput epididymidis (5.8 +/- 1.7 cells per cross-sectional duct) and only occasionally in the corpus epididymidis. The morphologic appearance of AMRCs varies from slender cells extending from the basement membrane to the lumen to apical cells without apparent contact with the basement membrane. The former display a round pale nucleus located in the middle of the epithelium; the apical cells have a dark nucleus, which, surrounded by a narrow cytoplasmic band, protrudes into the lumen. The cytoplasm of AMRCs is electron-dense and contains numerous mitochondria surrounded by rough endoplasmic reticulum cisternae. In the apical portion, there are lysosomes, vesicles with an electron-dense granule, and vacuoles showing a variable size and content. The stereocilia are shorter and less numerous than those of the PCs. The AMRCs are similar to the PCs in the intensely positive reaction for the enzymatic activity acid phosphatase, as well as in the lack of reaction for alkaline phosphatase and phosphorylase activities. AMRCs differ from PCs in: (1) a more intense reaction to the enzymatic activities ATPase, NADP, and succinic dehydrogenease, (2) a more intense immunostaining by AE1/AE3 and Ks4.62 anti-cytokeratin antibodies, and anti-estradiol receptor protein (D5) antibodies, and (3) a lower staining affinity for epithelial membrane antigen (EMA) antibodies. No positive immunostaining for the anti-cytokeratin Ks8.6 antibodies was observed in either AMRCs or PCs.

Role of epithelial clear cells of the rat epididymis in the disposal of the contents of cytoplasmic droplets detached from spermatozoa

Upon release from the seminiferous epithelium, spermatoza show a small droplet of cytoplasm attached to the neck region. During transit of spermatozoa in the caput epididymidis, this cytoplasmic droplet migrates along the middle piece of the flagellum. In the corpus epididymidis, the droplet shows a lateral displacement, while in the cauda epididymidis it detaches from the spermatozoon. In the electron microscope, cytoplasmic droplets attached to spermatozoa were seen to contain numerous, short, straight or C-shaped, flattened membranous elements referred to as lamellae, small vesicles, and small particles (35-nm diameter) with a diffuse wall showing no apparent unit membrane. The lamellae were stacked closely on one another or arranged in a loose array. Structurally as well as cytochemically, with different cytochemical markers, the lamellae and vesicular elements failed to show any evidence of being components of the Golgi apparatus or elements of the endoplasmic reticulum. The lamellae, vesicular elements, and 35-nm particles were also seen free in the lumen of the corpus epididymidis but were especially prominent in the cauda epididymidis at a time when droplets were being released from spermatozoa. The lumen of the epididymis, as spermatozoa passed from the caput to the cauda epididymidis, was also noted to acquire progressively a flocculent background material. The epididymal epithelium is composed predominantly of principal and clear cells. The endocytic activity of clear cells was examined in rats at different time intervals after a single injection of cationic ferritin into the lumen of the cauda epididymidis. At 2 min the tracer was bound to the microvilli of these cells and was also observed within large coated and uncoated pits, subsurface coated vesicles, and numerous subsurface small uncoated vesicular membranous elements (150-200-nm diameter). At 5 min, in addition to the above structures, the tracer was present in endosomes, while at 15 and 30 min, pale and dense multivesicular bodies appeared labeled, respectively. At 1 and 2 hr, but more so at 6 hr large dense membrane-bound bodies identified cytochemically as secondary lysosomes became labeled. All of the above endocytic structures were also seen to contain the 35-nm particles, flattened or vesicular membranous profiles, and a fine flocculent background material reminiscent of those seen free in the lumen or found in cytoplasmic droplets attached to spermatozoa. (ABSTRACT TRUNCATED AT 400 WORDS)

Immunocytochemical localization of the major glycoprotein of epididymal fluid from the cauda in the epithelium of the mouse epididymis

The most abundant protein in fluid from the mouse cauda epididymidis, designated CP 27, is a glycoprotein that migrates at approximately 27000 daltons on SDS-polyacrylamide gels. Samples of CP 27 were isolated by preparative gel electrophoresis and were used to raise a guinea-pig polyclonal antiserum, which reacted with a single band on western blots of caudal epididymal fluid. This antiserum was used for immunocytochemical localization of CP 27 in histological sections of mouse epididymis using the peroxidase-antiperoxidase and protein A-gold methods. The most proximal staining with anti-CP 27 was in segment 6 of the distal caput epididymidis, where the lumen and a portion of the supranuclear cytoplasm of principal cells were stained. In contrast, in the distal corpus and cauda epididymidis (segments 8-11), there was pronounced staining of the luminal contents, sterocilia, and scattered cells identified as the "light" cells of the epididymal epithelium. Although CP 27 was found in the epididymal lumen of all segments distal to segment 6, the intensity of staining appeared to decline distally in the cauda epididymidis. Control sections exposed to pre-immune serum instead of anti-CP 27 showed no reaction. The results suggest that CP 27, the major glycoprotein of cauda epididymal fluid, is synthesized by principal cells of segment 6 of the distal caput epididymidis. CP 27 may be among the substances absorbed from the lumen by the light cells of the distal epididymis.

The intracellular pathway of antagglutinin secretion in the boar caput epididymidis as revealed by immunogold labelling

Antagglutinin, a specific protein synthesized by the boar epididymis, was localized by an ultrastructural immunogold-labeling procedure in the principal cells of the three regions of the caput epididymidis, most notably at the sites of synthesis and secretion. The intensity of the reaction was variable in the three epididymal zones. Labeling was of low intensity in the proximal and middle caput, except in the granules of the latter. These granular "storage sites" did not correspond to typical secretory granules but appeared to be intracellular sites of degradation of this protein. In the distal caput, which was devoid of these granules, intense secretory activity for antagglutinin was detected. Few gold particles were localized in the RER profiles but labeling was detected in the Golgi zone, in numerous dense vesicles, in structures distributed between the Golgi zone and the apex of the cell, and in the epididymal lumen. This study has enabled us to visualize immunocytochemically antagglutinin along its intracellular secretory pathway, i.e. at the site of its synthesis, during its passage via the Golgi zone, and its intracellular transport to the lumen.

Protein transport to the epididymal lumen

Experiments were performed to clarify the debate over the entry of circulating proteins into the epididymal lumen by use of the marker horseradish peroxidase (HRP). Epididymal tubules from the caput epididymidis of the rat were immersed in medium TC 199 containing HRP (3.5 mg/ml) for 5 min to 3 h at 33 degrees C. Sections were examined for the presence of tracer within the epithelial cells by electron microscopy. From 5 min to 3 h, vesicles containing peroxidase reaction products were found throughout the cytoplasm of the principal cells. Vesicles occurred close to both the basal and apical membranes, and many were found opening into the interstitial space and lumen, depending on the length of incubation. By 5 min labelled vesicles were infrequently found in the apical part of the cells. Reaction product was observed in the epididymal lumen adhering to the microvilli from 30 min of incubation onwards. At all periods of incubation peroxidase was present at the base of the epithelium and between the cells, but it was never found within the tight junctional complexes, and no reaction deposits were found within epithelial cells of tubules incubated in the absence of peroxidase. It is concluded that large molecules leaving the capillaries may enter the epididymal lumen in the caput by means of fluid-phase endocytosis.

Electrophoretic characterization of mouse epididymal esterases in inbred lines and in a natural population

Esterase isozymes were studied in mouse epididymis of two inbred strains (C57BL, DBA/2) and in a natural population (Swiss OF1), by using vertical polyacrylamide gel electrophoresis and staining with alpha or beta-naphthyl acetate as a substrate. Eighteen (C57BL), 17 (DBA/2) or 16 (Swiss OF1) epididymal isozymes were separated; four were common to the testis, and five to both the testis and the serum. The use of different inhibitors showed that carboxylesterase activities account for the greater part of the total epididymis non-specific esterase activity. This comparative study revealed minor interspecies variations since only two isozymes were not expressed in the same manner in the three populations examined. Among the nine isozymes which appeared solely in the epididymis, the profiles varied between tissues and fluids as well as between the proximal part in which sperm maturation occurs and the distal part where sperm storage takes place. The variations proceeded from the relative activity of isozymes and the presence or absence of some of them; two characterized the proximal part and one the distal part in the three species. By comparing testis and epididymal tissues and fluids, it is suggested that the isozymes found in epididymal fluids originated from the testis, the epididymal epithelium or both. In addition to this epididymal secretory function, the lack in the fluid of the distal part of one isozyme identified in the testis, and two in the proximal part may also provide evidence for its reabsorptive function.

Structure and function of the epididymis

Testicular spermatozoa are functionally immature in that they cannot fertilize ova. It was first demonstrated by Young that spermatozoa undergo certain changes as they migrate through the epididymis. He proposed that spermatozoa ripen during epididymal transit. It is now known that specific maturational changes occur in spermatozoa during epididymal transit which result in their developing the ability to fertilize ova. Concomitant with this functional maturity are changes in spermatozoal morphology, motility, chemistry, permeability, density and metabolism. It is apparent that in some way not understood these changes are necessary for sperm to achieve the ability to complete the fertilization process. When these mechanisms are understood, we may be able to effectively treat conditions such as necrospermia or abnormally low sperm motility. Furthermore, with the development of the hamster-egg penetration test a "new" type of male infertility has become evident in recent years; the inability of otherwise normal sperm to penetrate an ovum. It is during epididymal transit that this ability is normally acquired. Thus, any insight into how sperm attain the capacity to penetrate an ovum could lead to an effective treatment of patients whose sperm do not have this ability. In addition, the epididymis holds significant promise as the site of action for a male contraceptive. Thus, it is the purpose of this review to describe the structure and function of the mammalian epididymis with particular emphasis on the factors regulating sperm maturation.

Comparison of lectin-staining pattern in testis and epididymis of gerbil, guinea pig, mouse, and nutria

The testis and epididymis of gerbil, guinea pig, nutria, and mouse were studied after staining with seven rhodamine-conjugated lectins to disclose the distribution of glycoproteins with different sugar residues. In the testis, the lectins showed a variable affinity for Leydig cells, tubular basement membrane, cytoplasm, acrosome, and plasma membrane of maturing spermatids as well as for Sertoli cell extensions. During acrosomal development, the staining pattern showed characteristic changes with different lectins indicating a gradual processing of the glycoprotein components. The staining in the Sertoli cell extensions displayed a cyclic change linked with the release of spermatozoa. A nuclear staining was prominent in zygotene and pachytene spermatocytes in the mouse, weak in the nutria, but absent in gerbil and guinea pig. The principal cells of epididymis showed a lectin-stained Golgi region as well as a similar staining in the apical surface, microvilli, and tubular contents. This staining was most prominent in the caput/corpus regions with some interspecies differences indicating the epididymal areas active in secretion. Narrow cells active in absorption of testis-derived material were lectin-positive in the initial segment of mouse, gerbil, and nutria epididymis. Large light cells with a strong affinity for some lectins were found in the proximal cauda of gerbil and guinea-pig epididymis. In the nutria, corresponding cells were arranged as islands within the low epithelium. The distal cauda of mouse, gerbil, and nutria was the site for lectin-stained light cells interspersed among the low principal cells. It is concluded that the high and low light cells may be active in the absorption and phagocytosis of residual bodies/cytoplasmic droplets and surplus epididymal secretory material, respectively. Thus, labeled lectins formed a useful tool in the analysis of glycoprotein distribution, processing, secretion, absorption, and degradation in the male reproductive tissues.

Subcellular distribution of the nonspecific esterase in the mouse epididymis with special reference to regional differences

The subcellular distribution of esterases was studied in mouse epididymis by using 5-bromo-indoxyl-acetate as a substrate. In all the cells of the duct, a low level of esterase activity was detected except in one of the five segments of the head--segment IV; in one of the three types of apical cells--the "prominent cells"; and in the "clear cells" scattered in the middle and distal parts. In these cells, the intensity of the reaction was high. The reaction product was consistently found in the endoplasmic reticulum and was more abundant in cells showing a high level of activity than in others. In cells with low esterase activity, the reaction was mainly restricted to this organelle. In highly active cells, the spectrum of subcellular locations was selectively enlarged and esterase was demonstrated in almost all cell compartments, including the cell membrane, nuclear envelope, mitochondria, lytic structures, and, more rarely in the Golgi apparatus or microvilli. These locations were dependent on cell type. A weak enzyme activity also appeared on mature spermatozoa.

Selective luminal absorption of L-carnitine from the proximal regions of the rat epididymis. Possible relationships to development of sperm motility

The absorption of L-carnitine from the duct of the proximal regions of the rat epididymis was investigated using a stopped-flow, split-droplet microperfusion technique. L-carnitine was absorbed from the duct of the proximal caput epididymidis by a time-dependent and saturable transport system (Km = 25 micron; Vmax = 0.65 pmoles absorbed/min/mm3 tubular volume). Furthermore, absorption appeared to be primarily sodium-independent, although the existence of a minor sodium-dependent pathway cannot be ruled out. A similar transport system was not evident along the distal caput epididymidis, where absorption of L-carnitine was attributable to passive diffusion only. The inward and outward movement of L-carnitine across the epithelium of the proximal and distal caput epididymidis appears to be regulated so that the spermatozoa come into contact with high levels of L-carnitine in the distal caput region.