Quantitative （stereological） study of incomplete spermatogenic suppression induced by testosterone undecanoate injection in rats

Aim: To evaluate the key lesions in spermatogenesis suppressed partially by testosterone undecanoate(TU) treatment. Methods: Adult male SD rats were treated with vehicle or TU (19 mg/kg) injection (i.m.) every 15 days for 130 days. The numbers of all types of cells (nuclei) in the seminiferous tubules and the interstitial tissue were estimated using a contemporary stereological tool, the optical disector. Results: In response to TU treatment, the numbers of non-type B spermatogonia, type B sperrnatogonia and late elongated spermatids per testis were reduced to 51%, 66% and 14% of the controls, respectively. The conversion ratios from type B spermatogonia to early spermatocytes and pachytene spermatocytes were not significantly affected and the ratios to the later germ cell types fell to 51%-65% of the controls. Less than 1.0 % of immature round spermatids were seen sloughing into the tubule lumen, 4.0% of elongated spermatids retained in the seminiferous epithelium, and about half of the elongated spermatid nuclei appreciably malformed. Leydig cells were atrophied but their number and the peritubular myoid cell number per testis were unchanged. Conclusion: Double inhibition of spermatogenesis (i.e. inhibition at spermiation and spermatogonial conversion to type B spermatogonia), a scenario seen in the monkey and human following gonadotrophin withdrawal, was not sufficiently effective for a complete spermatogenic suppression in the rat after TU treatment, probably due to ineffective inhibition of the Leydig cell population and therefore the intra-testicular test-osterone levels. (Asian J Androl 2004 Dec; 6: 291-297)     

中老龄雄性大鼠雄激素减低与代谢关系及发病机制的研究

目的:研究中老龄雄性大鼠雄激素减低与代谢的关系,雄激素减低发生的机制,尤其是睾丸间质细胞数量、形态及分泌功能的变化。方法:分别取9月龄(中青龄)和12、15、18、21月龄(中老龄)雄性SD大鼠每月龄组6只,静脉血检测大鼠代谢指标的变化,包括高密度脂蛋白(HDL)、低密度脂蛋白(LDL)、甘油三酯(TG)、总胆固醇(TC)、血糖(Glu)、胰岛素(INS)、胰高血糖素(IRG)、瘦素(LP)含量;检测大鼠血清激素的改变,包括总睾酮(tT)、黄体生成素(LH)、卵泡刺激素(FSH);通过组织切片观察大鼠睾丸间质细胞形态学变化;使用人绒毛膜促性腺激素(hCG)、毛喉素(Forskolin)刺激体外培养的大鼠睾丸间质细胞,比较培养液中睾酮(T)浓度;采用脱氧核苷酸转移酶介导的dUTP缺口末端标记(TUNEL)法检测大鼠睾丸间质细胞凋亡率;分离称重内脏脂肪,计算内脏脂肪/体重比及Lee's指数。结果:中老龄大鼠的血清tT[(1.26±0.65)ng/ml]比中青龄大鼠[(3.24±0.38)ng/ml]显著降低(P<0.01);中老龄大鼠睾酮分泌指数(TSI)[(0.07±0.05)ng/mIU]比中青龄大鼠[(0.21±0.01)ng/mIU]显著降低(P<0.01);不同年龄大鼠睾丸间质细胞形态有较显著差异;体外培养的中老龄大鼠睾丸间质细胞在24、48、72 h内T分泌量均显著低于中青龄大鼠(P<0.05);中老龄大鼠睾丸间质细胞TUNEL阳性率[(17.36±1.31)%]比中青龄大鼠[(7.02±1.05)%]显著升高(P<0.01);中老龄组和中青龄组大鼠IRG、HDL、LDL、TG、TC及内脏脂肪含量有显著性差异(P<0.05)。结论:中老龄大鼠血清tT浓度显著低于中青龄大鼠,代谢指标随血清tT降低发生规律改变;中老龄大鼠雄激素减低可能与睾丸间质细胞分泌功能衰退、间质细胞数量减少及垂体功能衰退有关。     

Feeding hydroalcoholic extract powder of Lepidium meyenii (maca) increases serum testosterone concentration and enhances steroidogenic ability of Leydig cells in male rats

Although Lepidium meyenii (maca), a plant growing in Peru's central Andes, has been traditionally used for enhancing fertility and reproductive performance in domestic animals and human beings, effects of maca on reproductive organs are still unclear. This study examined whether feeding the hydroalcoholic extract powder of maca for 6 weeks affects weight of the reproductive organs, serum concentrations of testosterone and luteinising hormone (LH), number and cytoplasmic area of immunohistochemically stained Leydig cells, and steroidogenesis of cultured Leydig cells in 8‐week‐old male rats. Feeding the extract powder increased weight of seminal vesicles, serum testosterone level and cytoplasmic area of Leydig cells when compared with controls. Weight of prostate gland, serum LH concentration and number of Leydig cells were not affected by the maca treatment. The testosterone production by Leydig cells significantly increased when cultured with 22R‐hydroxycholesterol or pregnenolone and tended to increase when cultured with hCG by feeding the extract powder. The results show that feeding the hydroalcoholic extract powder of maca for 6 weeks increases serum testosterone concentration associated with seminal vesicle stimulation in male rats, and this increase in testosterone level may be related to the enhanced ability of testosterone production by Leydig cells especially in the metabolic process following cholesterol.     

Effects of local heating of the testes on the concentration of testosterone in jugular and testicular venous blood of rats and on testosterone production in vitro

Heating both testes of rats to between 39 degrees C and 41 degrees C for 30 min was apparently without effect 21 days later, but heating to between 41.5 degrees C and 43 degrees C for 30 min resulted in a significant drop in testis weight accompanied by significant rises in the serum levels of LH and FSH. There were no changes in serum testosterone concentration in the peripheral circulation although there were increases in the concentration in testicular venous blood. The ability of the heated testis to secrete testosterone in vivo in response to maximal stimulation by hCG was reduced, as judged by testosterone levels in peripheral blood, while there was a supranormal increase in testosterone levels in testicular venous blood. Maximally stimulated testosterone production in vitro by the heated testis was supranormal whereas the basal production of testosterone per testis was not different from control values. Therefore, it appears that the testosterone produced by Leydig cells from heated testes may not be secreted as effectively as in normal testes.     

Increased testosterone production in vitro by Leydig cells from rats with severe autoimmune orchitis

We have previously observed (M. O. Suescun et al. , 1994, Journal of Andrology , 15 , 442–448) that rats with autoimmune orchitis (EAO) exhibit increased testosterone production in vitro by isolated testes. The aim of the present study was to determine whether the increase in testosterone production correlated with an enhanced number of Leydig cells and/or enhanced steroidogenic capacity per Leydig cell. For this purpose, EAO was induced in adult Sprague-Dawley rats by active immunization with testicular homogenate and adjuvants. At 80 days after the primary immunization, 60% of rats presented with severe testicular damage characterized by sloughing of the seminiferous epithelium, seminiferous tubule atrophy and interstitial mononuclear cell infiltration. At 160 days after the first immunization, testicular lesions were more severe. A morphometric study, by light microscopy, showed an increase in the number of Leydig cells in rats with EAO (45% increase at 80 days and 50% at 160 days). By electronmicroscopy, testicular sections of rats with EAO revealed the presence of numerous Leydig cells closely associated with macrophages. Most Leydig cells exhibited ultrastructural features of active steroid secreting cells.
The steroidogenic capacity of Percoll-purified Leydig cells from testes of rats with EAO, killed at 80 and 160 days, was evaluated. Leydig cells from rats with EAO exhibited an enhanced steroidogenic response to hCG in vitro at 80 days (38%) and an increase in basal (77%) and post-hCG testosterone production (115%) at 160 days compared to controls. However, these cells were less sensitive to hCG. In conclusion, the results indicate that the enhancement of in-vitro testosterone production observed in rats with EAO is accounted for both by the increased number of Leydig cells and by the increased testosterone production of each Leydig cell.     

Recovery of lead‐induced suppressed reproduction in male rats by testosterone

The objective of the present study was to investigate the effects of testosterone in recuperation of lead‐induced suppressed reproduction in adult male rats. Lead acetate was administered orally to adult male rats (95 ± 5 days) at dosage level of 0.05 and 0.15% for 55 days through drinking water and injected intraperitoneally with either testoviron depot at a dose of 4.16 mg kg^?1 body weight or vehicle alone on days 1, 7 and 14 respectively. At the end of treatment, control and treated males were cohabited with untreated normal‐cycling females. After cohabitation for 5 days, all the male rats were killed and weights of reproductive organs were determined. Significant increase in the indices of testis, epididymis, seminal vesicles, vas deferens and prostate glands was observed in testosterone (T)‐treated rats when compared to those of lead‐exposed rats. Testosterone treatment significantly increased epididymal sperm count, motile spermatozoa, viable spermatozoa and HOS tail‐coiled spermatozoa and also the activity levels of testicular 3β‐ and 17β‐hydroxysteroid dehydrogenases when compared to those of lead‐exposed males. From the results, it can be hypothesised that supplementation of testosterone mitigated lead‐induced suppressed reproduction in male rats.     

The importance of the Leydig cells in the vascular response to hCG in the rat testis

The increase in permeability of the testicular blood vessels following an injection of hCG into rats is abolished completely if the animals are treated 3 days earlier with ethane dimethane sulphonate (EDS), a compound that effectively eliminates Leydig cells from the testes. As there is other evidence that androgens or prostaglandins are not involved in this vascular response, further studies will be necessary to determine whether these data mean that another vasoactive substance is secreted by the Leydig cells or whether the EDS also eliminates other cells besides the Leydig cells, for example the mast cells found in the vicinity of the testicular artery.     

The temporal response of rat testes to hCG stimulation during sexual maturation

Serum testosterone responses to a single sc injection of hCG (25 IU/100 g body weight) were monitored for 5 days in rats throughout sexual maturation (22-70 days). Two hours after hCG injection serum testosterone levels rose in 22, 37 and 53 day-old animals and remained elevated for 2 days, returning to control levels on day 3. This response differed markedly from the biphasic secretion of testosterone reported for adult animals. In 70 day-old animals the serum testosterone response approached that seen in adult animals. Testosterone levels were elevated 2 h after hCG injection (25.4 +/- 2.5 ng/ml) and declined significantly at 12 and 24 h to 17.1 +/- 1.0 and 16.1 +/- 3.4 ng/ml, respectively. Testosterone levels tended to increase again on days 2 and 3 (19.9 +/- 2.8 and 21.1 +/- 3.5 ng/ml, respectively) but the increase was not statistically significant. This response differed markedly to the biphasic secretion of testosterone reported for adult animals. In vitro patterns of basal and hCG-stimulated testosterone secretion by decapsulated testes following a single hCG injection also changed during sexual maturation. In 22 day-old animals the testes exhibited refractoriness to in vitro hCG stimulation at 12 h, but testes from 37 day old rats were refractory from 2 to 24 h. In vitro testosterone responses of testes from 53 and 70 day-old rats were similar to that reported for adult rats with a period of refractoriness from 12 h to 2 days. This study demonstrates that during sexual maturation in the rat alterations occur in the temporal patterns of testosterone secretion in vivo and in vitro following hCG stimulation.     

Reversible effect of testosterone undecanoate injection on spermatogenesis in rats

Aim: To study the effect of testosterone undecanoate (TU) injection on spermatogenesis in rats. Methods: Twenty adult SD rats received vehicle or TU (8 mg/kg, 19 mg/kg or 025 mg/kg) injection, im, every 15 days for days, and another 38 animals received similar treatments for 130 days with half of them undergoing a recovery phase of 120 days (5 rats for each treatment). At the end of the treatment, testes were removed and the diameter of the seminiferous tubules and the number of late elongated spermatids ( steps 15 - 19 ) per testis were estimated with stereological methods as a measure of the spermatogenic efficiency. Results: Low dose (8 mg/kg) TU treatment virtually had no effect on spermatogenesis. A dose of 19 mg/kg slightly suppressed spermatogenesis 60 days after treatment, and severe suppression occurred after another 70 days of dosing. Spermatogenesis was completely recovered at the end of the recovery phase. Large dose (625 mg/kg) TU treatment did not significantly affect spermatogenesis and was well tolerated by animals. Conclusion: TU injection reversibly suppresses spermatogenesis in rats.     

Long‐term feeding of hydroalcoholic extract powder of Lepidium meyenii (maca) enhances the steroidogenic ability of Leydig cells to alleviate its decline with ageing in male rats

This study examined whether feeding hydroalcoholic extract of Lepidium meyenii (maca) to 8‐week‐old (sexually maturing) or 18‐week‐old (mature) male rats for more than a half year affects serum testosterone concentration and testosterone production by Leydig cells cultured with hCG, 22R‐hydroxycholesterol or pregnenolone. Testosterone concentration was determined in the serum samples obtained before and 6, 12, 18 and 24 weeks after the feeding, and it was significantly increased only at the 6 weeks in the group fed with the maca extract to maturing rats when it was compared with controls. Testosterone production by Leydig cells significantly increased when cultured with hCG by feeding the maca extract to maturing rats for 27 weeks (35 weeks of age) and when cultured with 22R‐hydroxycholesterol by feeding it to mature rats for 30 weeks (48 weeks of age). Overall testosterone production by cultured Leydig cells decreased to about a half from 35 to 48 weeks of age. These results suggest that feeding the maca extract for a long time to male rats may enhance the steroidogenic ability of Leydig cells to alleviate its decline with ageing, whereas it may cause only a transient increase in blood testosterone concentration in sexually maturing male rats.     

内皮素对大鼠睾丸间质细胞睾酮生成的影响

本研究采用大鼠睾丸间质细胞体外培养的技术 ,观察了内皮素 1对离体间质细胞睾酮分泌的影响。研究发现 ,10 -9mol/L的ET 1可显著抑制间质细胞睾酮的基础分泌 (P <0 .0 5 ) ,并且ET 1对人绒毛膜促性腺激素 (hCG)刺激睾丸间质细胞睾酮分泌也有抑制作用 ,其有效抑制浓度为 10 -10 mol/L(P <0 .0 5 )。本实验结果提示 ,ET 1呈剂量依赖性抑制睾丸间质细胞睾酮的基础分泌和hCG诱导的分泌 ,ET 1可能为睾丸内的一种局部调节多肽     

DEHP对宫内仔鼠睾酮水平、IGF-1和 StAR mRNA表达的影响

目的 探讨不同剂量的邻苯二甲酸二(乙基)己酯(DEHP)对宫内期仔鼠睾酮水平及胰岛素样生长因子1(IGF-1)、类固醇激素合成急性调节蛋白(StAR)基因表达的影响.方法 雌性S-D大鼠24只,随机均分为4组:正常组、低剂量组、中剂量组和高剂量组.后三组给予不同剂量的DEHP灌胃,剂量分别为(10mg/kg·d-1)、(100mg/kg·d-1)、和(750mg/kg·d-1),时间自雌鼠怀孕后第一天开始至仔鼠出生后第一天止.正常组给予等剂量的玉米油.测量各组雄仔出生时肛门生殖器距离(AGD)和血清睾酮(T)水平;并用光镜和电镜观察仔鼠睾丸Leydig细胞形态学改变;Real-timePCR检测睾丸组织中IGF-1和StARmRNA表达水平.结果 与正常组比较,高剂量组AGD明显缩短,中剂量组AGD呈下降趋势;低剂量组T水平升高、中高剂量组T水平降低;低、中、高剂量组StARmRNA表达下降;低剂量组IGF-1mRNA表达升高,中、高剂量组表达下降.光镜下见随着剂量的升高,睾丸Leydig细胞聚集越明显,高剂量组Leydig细胞呈瘤样聚集;电镜下见低剂量组Leydig细胞线粒体和滑面内质网增多,中、高剂量组均减少,并见脂滴增加.结论 DEHP可以影响富内仔鼠睾酮的合成,不同剂量具有不同的效应,其机制可能与DEHP影响IGF-1和StARmRNA表达有关.     

Effect of clomiphene treatment on the human testicular response to a single dose of hCG

The effect of antioestrogen treatment on the human testicular response to hCG was investigated in 17 adult men to further clarify the role of endogenous oestradiol in the regulation of testicular steroidogenesis. Clomiphene citrate was administered in 2 different modes. Group 1 (n = 8) was treated for 6 days (100 mg of the antioestrogen once a day) and a single dose of hCG (5000 IU im) was given at the beginning of the experiment. In group 2 (n = 9), the treatment was started 7 days prior to the hCG injection and was continued for additional 6 days. In both groups peripheral blood samples were collected up to 6 days after hCG, and the sera were analysed for FSH, prolactin and 8 steroids. In group 1, the steroidogenic response was identical to that found previously in untreated men. In group 2, the 7-day treatment with clomiphene citrate led to elevated serum concentrations of LH, FSH, pregnenolone, 17-hydroxyprogesterone, dehydroepiandrosterone, androstenedione, testosterone, 5α-dihydrotestosterone and oestradiol. When compared with these elevated values, the responses of serum 17-hydroxyprogesterone. dehydroepiandrosterone, androstenedione and testosterone to hCG were diminished. The ratios of the steroid concentrations support previous reports that hCG-induced inhibition of 17-hydroxylase, 17–20 desmolase and 3β-hydroxysteroid dehydrogenase-Δ^4–5 isomerase is decreased during antioestrogen administration. This further substantiates the idea of a central role for endogenous testicular oestradiol in the mediation of steroidogenic lesions following acute large doses of hCG.     

Annexin5对雄性SD大鼠生殖相关指标和睾酮分泌的影响

目的 探讨膜联蚩白5(annexin5)对雄性SD大鼠体重、睾丸系数、附睾系数、精子相对计数和睾酮水平的影响.方法 给雄性SD大鼠腹腔注射3个不同剂量(7.5μg/kg、15μg/kg、30μg/kg)的annexin5,对照组腹腔汴射等晕的pH 8.0 Tris-HCI,1次/d,连续20d.分别称重对照组和实验组SD大鼠体重、睾丸、附睾,并对附睾尾进行精子计数.HE染色观察睾丸组织结构.运用化学发光法检测对照组和各实验组SD大鼠血清中睾酮浓度.结果 与对照组相比,15 μg/kg实验组大鼠附睾系数与精子相对计数均显著提高,分别提高了12.5%(131.8±9.6vs 117.2±5.9)(P<0.01)和31.4%(36.8±5.6vs 31.7±5.3)(P<0.05);其它剂量组与对照纰相比差异均无统计学意义(P>0.05).HE染色显示各剂量实验组与对照组相比,睾丸的形态结构没有发牛明显改变.7.5 μg/kg组和15 μg/kg组大鼠血清睾酮含量显著高十对照组,分别提高了35.5%(36.33±3.89vs26.82±3.75)(P<0.01)和82.8%(49.04±5.17vs26.82±3.75)(P<0.01),30 μg/kg组大鼠睾酮含量虽也有升高,但与对照组比较,结果无统计学意义(P>0.05).结论 腹腔注射annexin5能影响大鼠睾丸生精、附睾功能及睾酮水平,并与剂量有关.     

The effects of maternal exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin on testicular steroidogenesis in infantile male rats

Exposure of adult male animals to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) decreases serum androgen concentrations. Reduction in androgen levels after maternal exposure has also been reported, but these results have not been reproduced. We have earlier shown that TCDD stimulates rather than inhibits testosterone synthesis in the prenatal rat testis. The aim of the present study was to elucidate in utero-induced effects of TCDD on testicular steroidogenesis in the 14-day-old infant rats. At that time the foetal Leydig cell population is still the prevailing source of androgens. Pregnant Sprague-Dawley dams were given a single oral dose of TCDD (0, 0.04, 0.2, or 1.0 microg/kg) on day 13 of pregnancy. On postnatal day 14, the body weight of male offspring was reduced after exposure to 1.0 microg/kg TCDD (from 33.9 +/- 1.66 g to 31.6 +/- 2.67 g). Relative testis weight, plasma testosterone, luteinizing hormone and follicle-stimulating hormone levels remained unaltered in all exposure groups. Moreover, in ex vivo incubations, testosterone and cAMP production was not affected. StAR protein level in the freshly isolated testes was increased in the 0.2 microg/kg group, and seminiferous cord diameter in the 0.04 microg/kg group. The present study confirms our earlier findings in in utero TCDD-exposed foetal testis indicating that maternal TCDD exposure does not negatively influence the developmental testosterone production of foetal type Leydig cells in rats.     

Testicular blood flow and vasomotion can be maintained by testosterone in Leydig cell-depleted rats

The effect of testosterone supplementation on testicular blood flow, testicular vasomotion, the number of polymorphonuclear leucocytes (PMN's) in testicular blood vessels and prostatic blood flow were studied in rats in which the Leydig cell had been destroyed specifically by a single injection of ethane dimethylsulfonate (EDS). Other rats were supplemented with testosterone by subcutaneous injection of 25 mg testosterone propionate on days 1, 3 and 6. In some experiments, the effect of a single injection of 25 or 125 mg testosterone was studied. Testicular and prostatic blood flow and the number of PMN's in testicular blood vessels decreased, and vasomotion disappeared in Leydig cell-depleted rats, but testosterone supplementation restored all parameters to normal values. Moreover, a single injection of testosterone was able to restore testicular and prostatic blood flow to normal levels but had an inconsistent effect on vasomotion. These results suggest that testosterone may play a role in the physiological control of the testicular microcirculation.     

实验性精索静脉曲张大鼠血清及睾内睾酮的变化

目的:研究精索静脉曲张(VC)大鼠模型对血清T和睾丸内T的影响。方法:通过部分结扎左肾静脉建立SD大鼠VC模型20只;假手术组SD大鼠20只为对照组。模型建立后4、8周取静脉血,并取部分睾丸组织匀浆提取上清液,放免法测定血清及睾丸内T浓度。结果:血清T:实验组4、8周与同期对照组相比有下降趋势,但没有统计学意义。双侧睾丸内T水平:实验组4周与对照组4周相比下降,但无统计学意义(P>0.05);实验组8周与对照组8周相比下降,具有统计学意义(P<0.01)。结论:在8周内实验性大鼠VC并没有引起血清T的降低,但可以导致双侧睾丸内T降低。     

Isolation method of Leydig cells from mature male Djungarian hamsters (Phodopus sungorus) and their steroidogenic activity in vitro

For studies addressing the functions of Leydig cells, isolated cells are often better suited than intact animals. Here, the isolation procedure of Leydig cells from adult male Djungarian hamsters (Phodopus sungorus) is described. Cells were isolated using a procedure involving enzymatic dissociation and Percoll-gradient centrifugation. For each experiment, approximately 4.4 x 10(6) Leydig cells from six animals were obtained. The cells showed high steroidogenic responsiveness to physiological (ovine luteinizing hormone (oLH) and human chorionic gonadotropin (hCG)) and nonphysiological (forskolin) stimuli in vitro. Approximately 98% of cells were viable as assessed by trypan blue exclusion, and the purity varied from 80 to 95% as tested by 3 beta-hydroxysteroid dehydrogenase activity. Leydig cells were also identified by a bright yellow halo under phase-contrast microscopy. They contained numerous lipid droplets and showed round nuclei and prominent nucleoli. The cells responded to oLH, hCG and forskolin with an increased testosterone production in a dose-dependent manner. Dose-response curves in these studies suggest that Leydig cells of Djungarian hamsters undergo desensitization, probably due to down regulation of their LH/CG receptors.     

Morphometric analysis of the components of the neonatal and the adult rat testis interstitium

Leydig cells in the foetal rat testis are still present at birth and it has been hypothesized that they commence to degenerate immediately after birth, based on the decrease in their volume density (v/v%) with age. In this study the interstitium of the rat testis was studied quantitatively at 1, 5, 10, 15, 20 and 90 days after birth: the latter are considered to be adults. The absolute volumes of connective tissue cells and blood vessels increased with age. The absolute volumes of macrophages and lymphatic spaces were greater at 90 days than at any other age. The absolute volume of foetal Leydig cells per testis was unchanged from 1 to 15 days, despite a decrease in the % volume occupied per testis. The number of foetal Leydig cells per testis did not decline from days 1-20 although on day 20 an average foetal Leydig cell was smaller in volume than at earlier ages (days 1-15). Adult Leydig cells were recognized at day 10 and their absolute volume and number per testis increased from 15 to 90 days. Adult Leydig cells were similar in morphology to foetal Leydig cells at 20 days except for a reduced volume of cytoplasmic lipid.