Pathogenesis of male reproductive toxicity

Toxicologic disturbance of male reproductive function can occur at many sites and produce a range of effects, some primary and some secondary to the initial insult. The challenge to the toxicological pathologist is to identify the primary site of damage and provide an insight into the pathogenesis of the morphologic lesion or functional deficit. Target sites include the testis, the epididymis, the mature sperm, and the hormonal regulatory system. Detection of effects at these varied sites requires the measurement of multiple endpoints only 1 of which is histopathology, but once identified, careful microscopic examination of the early changes in lesion development can provide essential information on the probable target cell and possible mechanisms of toxicity. Chemicals that affect different cell types or specific cellular functions generally elicit predictable patterns of pathological changes that can be readily recognized. Understanding the pathogenesis, the likely reversibility and the significance of reproductive tract lesions is aided by a sound knowledge of the physiology of the testis and epididymis and, in particular, an understanding of the timing of sperm production and transport.     

亚硝酸盐暴露致雄性小鼠生殖毒性的探讨

目的 探讨亚硝酸盐暴露对雄性小鼠生殖毒性的分子机制。 方法 36只2月龄健康雄性小鼠,随机分为对照组(生理盐水）、低剂量组（60 mg/kg）和高剂量组（120 mg/kg）,每组12只进行亚硝酸盐灌胃3个月,观察小鼠的生长状况,HE染色法观察睾丸组织病理变化,免疫荧光和Western blotting方法分析检测睾丸组织细胞增殖与凋亡情况及DNA甲基化、组蛋白去乙酰化相关酶的表达情况。 结果 亚硝酸盐暴露组小鼠较对照组小鼠体重增加缓慢,睾丸指数降低（P<0.01）,形态发生病理性改变;亚硝酸盐暴露组小鼠睾丸组织细胞增殖较对照组明显减少,细胞凋亡较对照组明显增加（P<0.01）;同时DNA甲基化和组蛋白去乙酰化水平高于对照组（P<0.01）,且均具有剂量依赖性。 结论 亚硝酸盐暴露通过抑制雄性小鼠生长发育及睾丸生精细胞增殖,诱导睾丸生精细胞凋亡,造成雄性生殖毒性;DNA甲基化及组蛋白去乙酰化水平升高,提示表观遗传学可能参与了亚硝酸盐暴露对雄性生殖系统的损伤过程及调控机制。     

鼠巨细胞病毒感染对雄性小鼠生殖性激素水平的影响

目的研究鼠巨细胞病毒（MCMV）感染后雄性小鼠生殖性激素水平的变化，探讨MCMV感染影响雄性生殖功能的可能机制。方法选择无McMV活动感染的雄性小鼠，睾丸接种MCMV或不合MCMV的细胞培养液，设立实验组与对照组，采用放射免疫法检测接种后不同时段（小鼠一个生精周期内）的小鼠血清及睾丸组织内性激素含量，并进行比较。结果睾丸匀浆组织T浓度在MCMV感染第4～9d显著降低（P〈0．05），第14～21d有一短暂恢复过程，第38d又较对照组下降（P〈0.05）。血清LH浓度在MCMV感染的第4、9、14d显著升高（P〈0．05），其它时间点比较差异无统计学意义（P〉0．05）。而感染不同时期的血清T和FSH比较差异均无统计学意义（P〉0．05）。结论MCMV急性感染可引起雄鼠生殖内分泌激素水平的改变：通过影响其下丘脑-垂体-性腺轴的调节导致雄鼠生殖功能障碍。     

Toxic effects of citrinin on the male reproductive system in mice

This study investigated the effects of citrinin (CTN) on male mouse reproductive organs. Adult male mice were exposed to intraperitoneal injection of CTN at 0–6.25 mg/kg body weight daily for 7 days, and then mated with sexually mature untreated female mice. Reproductive organ relative weights, semen quality, serum testosterone concentrations and fertility of treated mice were assessed. CTN significantly increased relative weights of the testes, epididymis, seminal vesicle and preputial gland, increased the number of abnormal spermatozoa and decreased the number of live spermatozoa. A significantly lower pregnancy rate was observed when females were mated with CTN-exposed males. The histological results indicated that distance of testicular seminiferus tubule increased. The sperm count and serum testosterone concentrations were significantly reduced in a dose-dependent manner in mice treated with CTN. The results suggest that CTN has adverse effects on the reproductive system of adult male mice.     

Currently used alternatives to the Chernoff-Kavlock short-term in vivo reproductive toxicity assay

The Chernoff-Kavlock assay was initially designed to identify developmental toxins within a relatively short time frame, using a mammalian system. Although it has been used for initial prioritization of multiple agents studied concurrently or for dosage-range evaluations, it has not gained wide usage in a commercial setting. As proposed, use of the Chernoff-Kavlock assay in an industrial setting is relatively inefficient, in terms of animal usage and data produced, when compared with available alternative study designs. Only a single dosage level was studied, and the data obtained from the assay do not provide sufficient information to meet the minimum requirements of safety evaluations submitted for regulatory review. For these reasons, other methods of prioritization are generally used. Alternate methods used for initial screening and prioritization at our laboratory are: 1) the hydra developmental toxicity assay; and 2) a dosage-range study in rats. When the results of several pilot and definitive developmental toxicity assays performed in rats were compared, it appeared that the described pilot study served the dual functions of predicting and prioritizing the developmental hazard of the test agent and providing a dosage-range study that identified the appropriate dosages to be tested in the definitive study.     

Adverse effect of heroin hydrochloride on selected male reproductive parameters in mice

This study investigated the effects of heroin on selected male reproductive parameters in mice (Balb/C), e.g. body weight, testis weight, gonado-somatic index, sperm viability, concentration of serum testosterone and fertility rate. Seventy-two mice (36 male and 36 female) were used. The male mice were divided into two control and two experimental groups. For evaluation of fertility rate, three mice were chosen from each group. Experimental groups of heroin-dependant mice were divided into two groups: Experimental group I were given heroin at a dose of 5 mg/kg and experimental group II 5 mg/ml, intra-peritoneally twice daily for a period of 40 days. Results showed that heroin reduced sperm viability, serum testosterone concentration as well as body weight, testis weight and fertility as compared with control groups. However, no significant changes in the gonado-somatic index were observed. The data suggests that heroin may reduce some of the reproductive parameters in male mice.     

Successful contact sensitization to chromate in mice

Mice of the randomly bred strain ICR and of the inbred strain BALB/c could be successfully sensitized to chromate by repeated topical applications of a solution of potassium bichromate in dimethyl sulfoxide. The specificity of chromium sensitization was ascertained by ear tests, specific desensitization by intravenous injection of potassium bichromate and by histological ear sections showing marked infiltrates of leukocytes following ear application of chromium-dimethyl sulfoxide in already sensitized animals. It is concluded that mice may provide a useful experimental model for study of contact sensitivity to chromium.     

Protective effect of vitamin E and selenium combination on deltamethrin-induced reproductive toxicity in male rats

The current study was performed to assess the adverse effect of deltamethrin (DLM) on reproductive organs and fertility in male rats and to evaluate the protective role of vitamin E (VE) and selenium (Se) combination in alleviating the detrimental effect of DLM on male fertility. The lethal dose 50 (LD₅₀) of DLM for male rats was estimated at 6 mg/kg bwt. Thirty male albino rats (10-weeks-old) were divided into three groups (10 rats each): Control group was injected subcutaneously with 2 ml/kg bwt saline twice weekly and was daily administered 2 ml distilled water intra-gastrically; DLM-treated group received 0.6 mg/kg bwt (1/10 LD₅₀) DLM intra-gastrically once daily; DLM + VE/Se-treated group was injected subcutaneously with 1.2 mg/kg bwt Viteselen^®15 (VE/Se) twice weekly with concurrent daily administration of 0.6 mg/kg bwt (1/10 LD₅₀) DLM intra-gastrically. The experiment was conducted for 60 consecutive days. DLM caused a significant reduction in reproductive organs weights, sperm count, sperm motility percent, alive sperm percent, serum testosterone level and testicular reduced glutathione concentration (GSH). DLM-treated group showed a significant increase in sperm abnormalities and testicular malondialdehyde (MDA) concentrations. Histopathologically, DLM caused impairments in testes, epididymes and accessory sex glands. Conversely, treatment with VE/Se combination improved the reduction in the reproductive organs weights, sperm characteristics, DLM-induced oxidative damage of testes and the histopathological alterations of reproductive organs. Results indicate that DLM exerts significant harmful effects on male reproductive system and that the concurrent administration of VE/Se partly reduced the detrimental effects of DLM on male fertility.     

Tetracycline-induced reproductive toxicity in male rats: Effects of vitamin C and N-acetylcysteine

Tetracycline, a broad-spectrum antibiotic employed clinically in the treatment of bacteria infections, is known to cause a number of biochemical dysfunctions and suspected to induce testicular damage to animals and humans, but there is paucity of data on its effect and mechanism of action on the male reproductive system. The present study therefore evaluates its spermatotoxic and testicular toxicity in male rats and the chemoprotective effects of Vitamin C (Vit C) and N-acetylcysteine (NAC). Tetracycline was administered orally at the dose level of 28.6 mg/kg body weight per day in two equal divided doses (12h interval). Vit C and NAC were also administered orally to the rats at doses of 200 and 50 mg/kg body weight per day, respectively, for the 14 days of the experiment. While there was no change in the body weights of rats, tetracycline administration caused significant decrease in the relative weights of testis, epididymis and seminal vesicles (P<0.05). Administration of tetracycline caused a reduction in the epididymal sperm motility, percentage of live spermatozoa, sperm count, and an increase in abnormal sperm morphology, as well as induction of adverse histopathologic changes in the testes. While Vit C and NAC significantly mitigated the toxic effect of tetracycline on sperm parameters, the antioxidants did not improve the adverse histopathologic changes induced by antibiotic. Treatment of rats with tetracycline significantly decreased the activities of superoxide dismutase, catalase (CAT), glucose-6-phosphate dehydrogenase, glutathione-S-transferase (GST) and the levels of GSH and serum testosterone, while the activity of gamma-glutamyltranspeptidase and the formation of malondialdehyde (MDA) increased. Both Vit C and NAC significantly attenuated the toxic effects of tetracycline to the antioxidant and testicular marker enzymes as well as markers of oxidative stress. Collectively, the results suggest that therapeutic dose of tetracycline elicits spermatotoxic and testicular toxicity in male rats through induction of oxidative stress. The chemoprotective effects of Vit C and NAC during tetracycline treatment suggest that these antioxidants may find clinical application in cellular damage involving reactive oxygen species (ROS).     

褪黑素在丙烯酰胺诱发断乳期和成年雄性大鼠生殖毒性中的保护作用

目的探讨褪黑素(MT)对丙烯酰胺(AA)诱发断乳期和成年雄性大鼠生殖毒性的保护作用。方法断乳期和成年雄性大鼠均随机分为对照组、AA染毒组、MT预防组、AA加MT组(AA和MT同时处理28 d)、MT治疗组,每组各6只动物。实验结束后,取材各组大鼠的睾丸、附睾、前列腺和精囊,计算脏器系数,并利用HE染色观察上述组织的病理学改变。结果和对照组相比,AA染毒组断乳期大鼠睾丸的脏器系数均明显下降(P0.05);经MT处理组睾丸的脏器系数均出现了不同程度的升高(P0.05)。连续28 d给予MT,断乳期大鼠的前列腺和精囊会发生明显的萎缩现象,其中精囊更为明显,但在成年大鼠中未发现该种现象。组织病理学结果表明,AA染毒后,断乳期和成年大鼠的睾丸、附睾、前列腺均出现异常组织结构,经MT处理后,它们的上皮结构均有所改善,其中,MT治疗组的改善情况最为显著,但精囊中并发现有明显的异常现象。结论 MT对AA造成的断乳期和成年雄性大鼠生殖毒性损伤具有预防和缓解的作用。     

Perinatal exposure to genistein alters reproductive development and aggressive behavior in male mice

Exposure to endocrine disrupting chemicals adversely affects reproductive development and behavior in males. The goal of this study was to determine if exposure to genistein, an isoflavone found in soy, during early periods of sex differentiation alters reproductive development and behavior in male mice. Female C57BL/6 mice were fed a phytoestrogen-free diet supplemented with 0, 5 or 300 mg/kg of genistein throughout gestation and lactation. Anogenital distance (AGD) and body mass of male offspring was measured weekly from postnatal days 2-21, timing of preputial separation was assessed at puberty, and in adulthood, reproductive organ masses, sperm and testosterone production, and reproductive and aggressive behaviors were assessed. Exposure to genistein resulted in smaller AGD are reduced body mass, with the low-dose diet exerting a greater effect. Timing of preputial separation, adult reproductive behavior, sperm concentrations and testosterone production were not influenced by genistein treatment at either dose. Aggressive behaviors were decreased, whereas defensive behaviors were increased, in males that received the low-dose genistein diet. Exposure to genistein during critical periods of sex differentiation results in concurrent and persistent demasculinization in male mice. Phenotypic and behavioral abnormalities induced by genistein showed a non-monotonic response, where treatment with a low dose exerted a greater effect than treatment with a high dose of genistein. Given the popularity of soy infant formulas, the influence isoflavone exposure on reproductive and behavioral health in boys and men should be considered.     

Localization of estrogen and androgen receptors in male reproductive tissues of mice and rats

Using immunohistochemical methods, we studied the cell-type- and species-specific expressions of estrogen receptor (ER) isoforms (ER alpha and ER beta) and androgen receptors (ARs) in the male reproductive tract and accessory sex glands of mature mice and rats. ER alpha and ER beta showed cell-type- and species-specific distributions, respectively. In contrast, AR was localized in the epithelial and stroma cells of all tissues examined in this study, in both species. In mice, the epithelial cells of the ductuli efferentes showed a strong ER alpha-immunoreaction, and those of the caput epididymis, coagulating glands, and prostate also exhibited a positive reaction. Stroma cells, except in the ductuli efferentes, showed a positive ER alpha-immunostaining. In rats, ER alpha was detected in very few cell types: the epithelial cells of the ductuli efferentes showed a strong reaction, and the stroma cells of the ampullary and urethral glands exhibited a weak reaction. ER beta was localized in the epithelial cells of the prostate in mice, while the reaction was faint or negative in both the epithelial and stroma cells of other tissues. In rats, the ER beta-immunoreaction was strongest in the epithelial cells of the ventral prostate. The epithelial cells of the corpus and cauda epididymis, ductus deferens, and urethral glands, and the stroma cells of the urethral glands were also positively ER beta-immunostained. Almost the same AR distribution pattern was observed in both species. In particular, strong AR-immunostaining was present in the epithelial cells of the caput and corpus epididymis, seminal vesicle, and ventral prostate. These results indicate that species and tissues differences should be taken into careful consideration in assessing the physiological and pharmacological effects of sex steroids (particularly estrogens) on the reproductive tissues of male rodents.     

TCDD的生殖毒性作用对生殖系统的影响

环境类激素污染物中的二英的代表物质TCDD的毒性作用已成为人类健康研究的热点。本文就TCCD的生殖毒性表现 ,内分泌干扰作用及其可能作用机制的研究进展作一综述     

In vivo studies in male mice on the mutagenic effects of inorganic arsenic

The ability of sodium meta-arsenite (NaAsO₂) to produce geneticdamage in vivo has been evaluated in mice by the micronucleustest on bone marrow cells and the dominant lethality and spermabnormality assays on male germ cells. The doserelated linearincrease of micronuclei observed in somatic cells together withthe negative results obtained in reproductive cells suggestthat NaAsO₂, under the conditions of the present experiments,displays clastogenic properties in vivo in laboratory animals,but is unable to produce heritable damage.     

Overview of male reproductive pathology

An understanding of form and function is important for examination of the male reproductive tract. A basic understanding of spermatogenesis and hormonal function in the reproductive tract is essential for the pathologists in this evaluation. Gross and histologic reproductive changes need to be distinguished from normal variation and correlated with the reproductive status of the animal. This is especially important when correlating histologic changes with organ weight and other reproductive parameters, such as seminal analysis data. Sexual maturity of animals and tissue handing can impact interpretation. Sexual immaturity of preclinical safety animals can present challenges for accurate identification of compound-related changes. Likewise, proper handling of unfixed reproductive tissues and appropriate selection of a fixation protocol are important in avoiding artifacts that may interfere with the microscopic evaluation. The histopathology technician needs to recognize testicular landmarks that allow for correct orientation at trimming so the pathologist can assess not only the morphology of seminiferous tubules but also the outflow tract. For the most effective evaluation of the male reproductive tract, the testes and epididymides should be examined concurrently. Although the term "staging" is often used inappropriately, the pathologist should review testicular tissues in a "stage-aware" manner. This article reviews gross and histologic changes of the male reproductive tract as well as tissue orientation and fixation to assist in accurate interpretation of potential treatment-related changes in male reproduction.