Effects of cadmium upon the excurrent duct system of the rat testis

Development of spermatic granuloma in albino rats following administration of water extract of Heliotropium bacciferum Forssk

A spermatic granuloma is a chronic inflammatory reaction produced in response to extravasated sperm within the intertubular connective tissue. The present study investigates the possible toxic effects of water extract of Heliotropium bacciferum on the reproductive system of male albino rats and the associated potential for the development of spermatic granulomas. H. bacciferum is a herbal plant used in traditional medicine and reported to have cytotoxic effects due to pyrrolizidine alkaloids. Histological examinations revealed no changes in the tissues of the testes, although, some changes were detected in the cauda epididymis, the most important of which was the development of small lesions of spermatic granulomas. Clear gaps were observed between the epithelial linings of the epididymal tubules.

Interpreting histopathology in the epididymis

While most of this Special Issue is devoted to the testis (which is where most drug and chemically induced toxicity of the male reproductive tract is identified), being able to recognize and understand the potential effects of toxicants on the epididymis is immensely important and an area that is often overlooked. The epididymis is the organ where the post-testicular sperm differentiation occurs, through a complex and still not completely understood sperm maturation process, allowing them to fertilize the oocyte. Also in the epididymis, sperm are stored until ejaculation, while being protected from immunogenic reaction by a blood-epididymis barrier. From a toxicologic perspective the epididymis is inherently complicated as its structure and function can be altered both indirectly and directly. In this review we will discuss the factors that must be considered when attempting to distinguish between indirect and direct epididymal toxicity and highlight what is currently known about mechanisms of epididymal toxicants, using the rat as a reference model. We identify 2 distinguishable signature lesions - one representing androgen deprivation (secondary to Leydig cell toxicity in the testis) and another representing a direct acting toxicant. Other commonly observed alterations will also be shown and discussed. Finally, we point out that many of the key functions of the epididymis can be altered in the absence of a detectable change in tissue structure. Collectively, we hope this will provide pathologists with increased confidence in identification of epididymal toxicity and enable more informed guidance as mechanism of action is considered.

Disruption of estrogen receptor signaling and similar pathways in the efferent ductules and initial segment of the epididymis

Seminiferous tubular atrophy may involve indirectly the disruption of estrogen receptor-α (ESR1) function in efferent ductules of the testis. ESR1 helps to maintain fluid resorption by the ductal epithelium and the inhibition or stimulation of this activity in rodent species will lead to fluid accumulation in the lumen. If not resolved, the abnormal buildup of fluid in the head of the epididymis and efferent ductules becomes a serious problem for the testis, as it leads to an increase in testis weight, tubular dilation and seminiferous epithelial degeneration, as well as testicular atrophy. The same sequence of pathogenesis occurs if the efferent ductule lumen becomes occluded. This review provides an introduction to the role of estrogen in the male reproductive tract but focuses on the various overlapping mechanisms that could induce efferent ductule dysfunction and fluid backpressure histopathology. Although efferent ductules are difficult to find, their inclusion in routine histological evaluations is recommended, as morphological images of these delicate tubules may be essential for understanding the mechanism of testicular injury, especially if dilations are observed in the rete testis and/or seminiferous tubules.

Signature Lesion:

The rete testis and efferent ductules can appear dilated, as if the lumens were greatly expanded with excess fluid or the accumulation of sperm. Because the efferent ductules resorb most of the fluid arriving from the rete testis lumen, one of two mechanisms is likely to be involved: a) reduced fluid uptake, which has been caused by the disruption in estrogen receptor signaling or associated pathways; or b) an increased rate of fluid resorption, which results in luminal occlusion. Both mechanisms can lead to a temporary increase in testicular weight, tubular dilation and atrophy of the seminiferous tubules.

Development of sperm granulomas in the epididymides of L-cysteine-treated rats

We investigated the histopathological effects of excess L-cysteine on the male rat reproductive tract during sexual maturation. Male 6-week-old Sprague-Dawley rats were injected intraperitoneally daily with L-cysteine, 1,000 mg/kg body weight, for 1, 2, 3, and 4 weeks. L-Cysteine-treated rats developed sperm granulomas in the epididymides at an incidence of 0% (0/6), 50% (3/6), 83% (5/6), and 100% (6/6) in rats examined at study weeks 1, 2, 3, and 4, respectively. These sperm granulomas were unilateral or bilateral, and most frequently involved the proximal cauda region of the epididymides. Interestingly, small ducts, indicative of immaturity, were seen frequently in L-cysteine-treated rats. These findings suggest that the maturation of epididymides in L-cysteine-treated rats might be delayed. Additionally, dilated ducts and interstitial edema, suggestive of an increase in intraluminal pressure, were seen often in the epididymides of L-cysteine-treated rats. Labeling spermatozoa and epithelial cells with monobromobimane indicated no influence of the thiol-disulfide status of L-cysteine to the epididymides. The testes and prostate glands also showed no effects, suggesting that inhibited epididymis maturation was not a result of hormonal deficiencies. We speculate that defective development of the ducts might result in aberrant fluid flow, leading to ductal rupture in the epididymides. In that case, sperm granulomas might form around leaked spermatozoa.

Relationship of interstitial edema with L-cysteine-induced sperm granulomas in the pubertal rat epididymis

Although the pathogenesis of sperm granulomas is complicated, the leakage of spermatozoa into extraluminal tissues is regarded as a crucial event. It has been previously shown that pubertal rats injected with L-cysteine develop interstitial edema followed by sperm granulomas in the epididymis. In this study we investigated the relationships between these two lesions in 6-week old rats given daily intraperitoneal injections of L-cysteine (1,000 mg/kg body weight) for 4 weeks. Rats were examined during weeks 0, 1, 2, 3 and 4 after the first injection. Interstitial edema (moderate or severe) and sperm granulomas were seen in the corpus and cauda epididymis of L-cysteine-treated rats in study weeks 2, 3, and 4. There was no marked alteration of basement membrane of the epididymal ducts in the edematous tissues as shown by immunohistochemistry with an antilaminin antibody. However, the extravasation of Evans blue dye given I hour before necropsy suggested that the severe interstitial edema was due to increased vascular permeability. In addition, a small number of neutrophils were seen in the edematous tissues, suggesting that they might play a role in the increased vascular permeability and leakage of epididymal fluid. Interestingly, slight interstitial edema was observed in the caput epididymis in both control and L-cysteine-treated rats in early study weeks 0, 1, and 2. It is speculated that this change was related to the leakage of epididymal fluid due to increased intraluminal pressure depending on rat epididymal maturation. Taken together, these findings suggest that the severe interstitial edema results from increased vascular permeability. This, along with increased intraluminal pressure, might be the trigger for duct rupture, the prerequisite for sperm granuloma formation associated with excessive doses of L-cysteine.

Effects of ischaemia on the caput epididymis and its relationship to higher epididymal obstruction: a qualitative study in the ram

The objective of this study was to determine if localized ischaemia of the caput epididymis in the ram causes morphological changes similar to those characteristic of higher epididymal obstruction in humans. This was tested by performing unilateral occlusion of the superior epididymal artery in 10 rams. At the end of 4 (n = 5) or 28 weeks (n = 4), rams were castrated and the testes and epididymides were weighed. Analysis of histological sections at the light microscope level provided quantitative data on lumen diameter and epithelial cell height of the efferent ducts. Qualitative analysis and specific histochemical stains for identification of lipofuscin pigment provided further information on tissue changes. Electron microscopy was performed on the efferent ducts to assess ultrastructural changes. The results revealed that localized ischaemia of the proximal epididymis caused a dramatic change in tubule calibre of the efferent ducts and initial segment resulting in obstruction of the distal lumina. These changes were more severe following 28 weeks of arterial occlusion. The epithelial cells of the proximal region showed an increase in the number of lysosomes and they became active in phagocytosis of spermatozoa. Lipofuscin pigment accumulated within the epithelial cells and also in macrophage-like cells that had invaded the lumina, interstitium and intra-epithelial regions of the ducts. On the basis of these observations we conclude that the tissue changes which occur in the ram epididymis as a result of localized ischaemia show a striking similarity to those seen in men exhibiting higher epididymal obstruction. This suggests the possible implication of vascular disorders in the aetiology of obstructive azoospermia in men.

Studies of lesions induced in the testis and epididymis of F-344 rats by inhaled methyl chloride

Experiments were carried out in rats to characterize the development of the testicular and epididymal lesions and any associated effects on reproductive hormones. Adult F-344 rats were exposed to 3500 ppm methyl chloride (MeCl) 6 hr/day for 5 days, not exposed for 3 days, and exposed again for 4 days. The first consistent testicular lesion was a delay in spermiation which appeared on Day 9. Subsequently, germinal epithelial vacuolation and cellular exfoliation became widespread as exposure continued. All animals killed after 19 days also displayed bilateral epididymal granulomas in regions 5 or 6 of the cauda epididymis. The nature and distribution of inflammatory cells indicated that the primary neutrophilic response may be against the tubular epithelium and not extravasated sperm. After 5 days of exposure, circulating testosterone was below 6 ng/ml (control: 120 +/- 31 ng/ml). Both MeCl exposed and control animals responded similarly to challenge with hCG and LHRH ethylamide, suggesting that Leydig cell and gonadotrope function was unaffected. It is proposed that MeCl acts centrally to lower circulating testosterone. Nonprotein sulfhydryls were depleted in liver, testis, and epididymis after MeCl exposure, but not in whole blood. This finding indicates that sulfhydryl depletion is not due to direct alkylation, but is enzymatically mediated. Sulfhydryl depletion did not correlate with lesion development. It was concluded that the initial testicular effects of MeCl are directed at either the late stage spermatids or the Sertoli cells with a resultant delay in spermiation.

Gametogenic count and histopathological effect of thorium nitrate and uranyl nitrate on mice testes

Daily intraperitoneal administration of aqueous solution of 0.05 m mole/100 g b. wt. of uranyl nitrate and thorium nitrate has been observed for 7 days. Marked reduction in the seminiferous tubule diameter and gametogenic count was observed. Signs of testicular necrosis, exfoliation of germ cells, and karyolysis and karyorrhexis were seen in most of the tutubles. Mononucleate and polynucleate giant cells were also observed indicating prolonged pathological condition.