Quercetin has a protective role on histopathological findings on testicular ischaemia-reperfusion injury in rats

We investigated the effects of quercetin on pathological findings on testicular ischaemia-reperfusion (I/R) injury in rats. Twenty-four male Wistar albino rats were randomly assigned into four groups: Group 1, control (n = 5); Group 2, sham (n = 4); Group 3, I/R (n = 8); and Group 4, I/R + quercetin (n = 7). Bilateral testicular artery and vein were occluded for 1 h, followed by reperfusion in I/R and I/R + quercetin animals. Quercetin (20 mg kg(-1) per day) was administrated once daily by gavage to Group 1 and Group 4, respectively, after reperfusion. At the end of the study, bilateral orchiectomies were performed for histopathologic examination. The tissue damage was evaluated with light microscopy. Normal inter-stitium and seminiferous tubules were observed in control group. In the sham group, rats were seen minimal oedema around the seminiferous tubules and congested vascular structures. In Group 3, oedema, vascular congestion and haemorrhage between seminiferous tubules were observed. In Group 4, histopathologic features were markedly less than Group 3 (P = 0.03). Our study demonstrated that quercetin seems to have a protective effect on testis histopathology in rats with testicular I/R.     

L-肉碱在奥硝唑所致大鼠睾丸和附睾损伤中的保护作用

目的:探讨L-肉碱(LC)在奥硝唑(ORN)所致大鼠附睾和睾丸损伤中的的保护作用。方法:40只雄性SD大鼠(200～230g)随机均分为5组:①A组:给予0.5%的羧甲基纤维素钠(溶剂)灌胃;②B组:每天给予400mg/kgORN灌胃;③C组:每天给予800mg/kgORN灌胃;④D组:每天给予[ORN(400mg/kg)+LC(100mg/kg)]灌胃;⑤E组:每天给予[ORN(800mg/kg)+LC(100mg/kg)]灌胃。上述各组均连续灌胃20d,末次给药24h后,所有大鼠麻醉后处死,分别取睾丸、附睾,进行称重和HE染色,计算睾丸、附睾系数并观察睾丸和附睾病理组织学改变。结果:①与A组相比,B组睾丸、附睾系数明显降低(P<0.05);而C组睾丸、附睾系数为极显著性降低(P<0.01);D组与A组相比无差异,E组与A组相比有极显著性差异(P<0.01);②HE染色显示,与A组相比,B组睾丸生精小管内各级生精细胞排列基本整齐,部分生精小管管腔内有脱落的生精细胞,附睾管腔中精子数目下降,有时可见散在的生精细胞;C组大鼠睾丸生精小管管腔内均可见坏死脱落的生精细胞,附睾管腔中精子数目明显减少,且有较多的非精子细胞成分。D组睾丸生精小管无明显改变,附睾管腔中精子数目也未见明显下降;E组睾丸生精小管管腔内精子数目减少,可见坏死脱落的生精细胞,附睾腔中精子数目明显减少,并伴有较多的非精子细胞成分。结论:奥硝唑(ORN)可导致雄性大鼠附睾和睾丸病理组织学改变,LC对ORN引起大鼠附睾和睾丸损伤具有一定的保护作用。     

The Anti-Reproductive Effects of Long Term Oral Administration of Cadmium on the Adult Male Rat

The toxic effects of prolonged oral administration of cadmium on gametogenic and endocrine function of testes of adult rats were investigated. The experimental animals received daily, for 3, 6, 12 or 15 months, pellets containing 8.8 mg or 88 mg of cadmium chloride per kg body weight.
The rats treated with the higher doses of cadmium for 12 and 15 months showed a marked reduction in absolute weight of testes accompanied by histological signs of impairment of seminiferous tubules. There were no necrotic changes but a number of cross-sections of seminiferous tubules were deprived of spermatocytes and spermatids, reaching about 50 per cent of the tubules in the rats treated with higher doses of cadmium. The appearance of histological changes in rats treated for 12 and 15 months correlated with cumulation step of cadmium in testes and with alterations in serum concentration of LH but not of testosterone. Therefore, we suppose that under these experimental conditions the impairment of seminiferous tubules was induced by the direct influence of cadmium on germinal epithelium beginning the moment when cadmium reaches an effectively toxic concentration in testis.     

Evaluation of antiandrogenic potentials of aqueous extract of Chromolaena odoratum (L.) K. R. leaves in male rats

The antiandrogenic effect of oral administration of aqueous extract of Chromolaena odoratum leaves (250 and 500 mg kg(-1) body weight) for 14 days in male albino rats was investigated. Forty-two white albino rats were randomly divided into three groups: A, B and C. Group A which served as the control received 1 ml of distilled water (the vehicle) twice daily for 14 days, whereas groups B and C were treated in the same way like the control except that the animals received 250 and 500 mg kg(-1) body weight of the plant extract respectively. Compared with the control, extract administration at 250 and 500 mg kg(-1) body weight revealed a significant reduction (P<0.05) in testicular body weight ratio, acid phosphatase activities, protein, cholesterol, glycogen, sialic acid and testosterone concentrations with a significant increase (P<0.05) in lactate dehydrogenase and gamma-glutamyl transferase activities. There was no significant change (P>0.05) in serum concentrations of follicle stimulating and luteinising hormones. Histological examination revealed disruption in the arrangement of seminiferous tubules with no distinct basement membrane. These changes were accompanied by reduction in the number of spermatozoa. All these results indicated that aqueous extract of C. odoratum leaves possesses antiandrogenic property by interfering with steroidogenesis at the testicular level and this will adversely affect the functional capacity of the testes and the fertility of the animal.     

Effects of the chronic use of finasteride on testicular weight and spermatogenesis in Wistar rats

OBJECTIVE: To evaluate spermatogenesis in rats chronically exposed to finasteride, as the recent use of finasteride in young men to prevent hair loss has raised concerns about chronic use and fertility. MATERIALS AND METHODS: Male Wistar rats (4 months old) were selected and divided into two groups. Group 1 (17 rats) received a finasteride suspension of 2 mg/kg/day in saline solution, 5 days/week for 10 months; group 2 (eight rats of the same age) were treated with placebo for the same period. At the end of the exposure the testes were weighed and processed for histological analysis. Spermatogenesis was evaluated as the mean number of seminiferous tubules with and without spermatozoids in their lumen, in five random fields on the same slide. Student's t-test was used to assess differences in the groups. RESULTS: In group 1, the mean (sd) weight of the testes was 1.55 (0.29) g and in group 2 1.58 (0.34) g (P>0.05). The histological analysis showed a mean of 13.35 (1.66) seminiferous tubules per field and 1.20 (3.30) tubules with no spermatozoids in group 1; in group 2 the respective values were 13.53 (1.46) and 0.06 (0.14) (P>0.05). CONCLUSION: Finasteride had no detectable effects on the quantitative and qualitative analysis of spermatogenesis in rats.     

The effects of human chorionic gonadotrophin on normal testicular tissue of rats: dose-dependence and reversibility

OBJECTIVE To investigate the effect of human chorionic gonadotrophin (hCG) on rat testicular tissue, and its reversibility and dose dependence. MATERIALS AND METHODS Male Wistar rats were assigned to groups (10 rats/group) receiving 10, 30 or 50 IU/kg hCG subcutaneously once daily for 15 days; 10 controls received subcutaneous isotonic saline. At 1 and 3 months later, five rats in each group were killed and their testes removed. The testes were examined histologically to measure seminiferous tubular diameter and germinal membrane thickness. RESULTS At 1 month after hCG administration, the mean germinal membrane thickness in the testicular tissues of the hCG-treated rats was significantly less than in control rats, and was also significantly different between all of the hCG-treated groups (P < 0.05). However, at 3 months after hCG administration, all histological variables were similar to those in control rats (P > 0.05), and the mean germinal membrane thickness at 3 months after hCG administration was larger than that at 1 month (P < 0.05). There were no significant differences in the mean seminiferous tubular diameter between hCG-treated rats and control rats. CONCLUSION hCG impairs seminiferous tubule histology in the 'normal' descended testes of rats. This effect was dose-dependent, and the changes were reversed at 3 months after treatment. Thus, although hCG therapy might affect the seminiferous tubules of contralateral descended testes in cryptorchid boys, these effects might be reversible.     

Antispermatogenic activity of Morinda lucida extract in male rats

Aim： To investigate the effect of Morinda lucida Benth （Rubiaceae） on the reproductive activity of male albino rats. Methods： Two groups of rats were treated with 400 mg/（kg.d） of Morinda lucida leaf extract for 4 and 13 weeks, respectively. The control rats received the vehicle. All the treated rats had corresponding recovery groups. At the end of each experimental period, animals were killed and organ weights, sperm characteristics, serum testosterone levels, histology of the testes and fertility were assessed. Results： Morinda lucida leaf extract did not cause any changes in body and somatic organ weights, but significantly increased the testis weight （P 〈 0.05）. The sperm motility and viability, and the epididymal sperm counts of rats treated for 13 weeks were significantly reduced （P 〈 0.05）. Sperm morphological abnormalities and serum testosterone levels were significantly increased （P 〈 0.05）. There were various degrees of damage to the seminiferous tubules. The extract reduced the fertility of the treated rats by reducing the litter size. Reversal of these changes, however, occurred after a period of time. Conclusion： The extract of Morinda lucida has reversible antispermatogenic properties.     

Effect of methanol extract of Ricinus communis seed on reproduction of male rats

Aim:To investigate the effect of methanol extract of Ricinus communis seed(RCE)on male rats reproductivefunctions.Methods:Thirty-two male albino rats were divided into four groups.Groups 1,2 and 3 were gavagedwith 0.2 mL of 2.5% tween 80(RCE vehicle;control)or 20 mg/(kg·d)and 40 mg/(kg·d)of RCE,respectively,for30 days,and group 4 was also gavaged with 40 mg/(kg·d)of RCE,but was allowed a recovery periold of 30 days.Five untreated female rats were cohabited with male rats in each group from day 25 of RCE treatment for 5 days,except group 4,where cohabitation began on day 25 of the recovery period.All male rats were sacrificed 24 h afterthe experiments.The female rats were laparatomized on day 19 of pregnancy and the number and weight of litterswere recorded.Results:There was a significant decrease(P<0.01)in the weight of the reproductive organs,sperm functions and serum levels of testosterone in RCE treated rats.There was disorganization in the cytoarchitec-ture of the testes,disruption of the seminiferous tubules and erosion of the germinal epithelium.The number andweight of litters of rats in groups 2 and 4 decreased significantly(P<0.05)but no changes were observed in group3.RCE caused no changes in liver,kidney,heart or body weights in male rats.Conclusion:RCE has a reversiblenegative impact on male reproductive functions,which appears to be mediated via gonadal disruption in testosteronesecretion.(Asian J Androl 2006 Jan;8:115-121)     

Testicular gametogenic and steroidogenic activities in chlorpyrifos insecticide-treated rats: a correlation study with testicular oxidative stress and role of antioxidant enzyme defence systems in Sprague-Dawley rats

The present works examined an adverse effect of chlorpyrifos insecticide on testes and lipid peroxidation at low doses (5 mg-10 mg kg(-1) body weight) and the role of antioxidant enzymes systems at higher doses (20-30 mg kg(-1) body weight) in albino rats. At low doses, reduction in plasma levels of testosterone and FSH and LH hormones along with the significant shrinkage of seminiferous tubules and gametogenic changes in germ cells were noticed. But these changes were restored with the revival of serum testosterone, FSH and LH along with regression of testis at higher doses. Similarly, level of testicular lipid peroxidation was elevated, whereas levels of antioxidant enzymes (superoxide dismutase, catalase and glutathione peroxidase) and steroidogenic enzymes activities (Δ(5) , 3β-hydroxysteroid dehydrogenase and 17β-hydroxysteroid dehydrogenase) were reduced significantly at low doses. But, rat testes showed a significant decrease in lipid peroxidation and concomitant increase in antioxidant enzymes and steroidogenic enzymes activities at higher doses. Results showed that at higher doses of chlorpyrifos treatments, rat testes were shown to trigger their natural defence mechanism which became operative possibly through corrective measure of synthesis of antioxidant defence enzymes and steroidogenic enzymes and pituitary gonadotrophins hormone feedback mechanisms.     

Effects of diazacholesterol dihydrochloride (SC-12937), an avian antifertility agent, on rat testis

The present study was undertaken to evaluate the effectiveness of an avian chemosterilant, 20, 25-diazacholesterol dihydrochloride (SC-12937), on the rat testis. Adult male rats were injected intraperitoneally with 10 mg (Group 1) or 30 mg (Group 2) of SC-12937/kg/d or with vehicle alone (Group 3) for 10 days, and were killed 24 hours after the last injection. A wide range of variation in the appearance of affected seminiferous tubules was observed in the testis of SC-12937-treated rats at both dose levels. This ranged from apparently normal-looking seminiferous tubules to almost completely atrophied tubules with no cells. Affected tubules exhibited intraepithelial vacuoles of varying size, multinucleated giant cells, germ cell exfoliation, and tubular atrophy. The presence of severely damaged and entirely normal seminiferous tubules adjacent to one another in the same section was noteworthy. The changes appeared to be dose-related. A greater number (34.6%) of affected tubules were observed in rats receiving 30 mg of SC-12937 compared with the ones receiving 10 mg of this compound (19.6%). The Sertoli cells also were affected by this drug and exhibited cytoplasmic vacuolation, a marked increase in the accumulation of lipid droplets and myeloid bodies. Necrotic Sertoli cells also were observed in the severely affected tubules. The possible mechanism of antispermatogenic action of SC-12937 in rats has been discussed briefly.     

Effect of Semecarpus anacardium fruits on reproductive function of male albino rats

Aim: To evaluate the effect of an ethanolic extract of Semecarpus anacardium fruits on spermatogenesis in albino rats. Methods: Male albino rats were fed with a 50 % ethanolic extract of Semecarpus anacardium fruit at 100 mg·kg-1.day-1, 200 mg·kg-1·day-1 and 300 mg·kg-1·day-1 for 60 days. Fertility test was performed after 60 days of treatment. Sperm motility and density were observed in the cauda epididymis. Biochemical and histological analyses of the blood and reproductive organs were done. Recovery of fertility was followed to evaluate the reversibility of drug action. Results: S. anacardium fruit extract administration resulted in spermatogenic arrest in albino rats. The sperm motility and density was reduced significantly. The RBC and WBC counts, haemoglobin, haematocrit, blood sugar and urea were found to be within the normal range in the whole blood. The protein, cholesterol and glycogen in the testes and the fructose in the seminal vesicle were significantly decreased after the treatment. T     

Assessment of germ cell apoptosis in cryptorchid rats

Aim: To investigate the relationship between germ cell degeneration and apoptosis in cryptorchid rats. Methods: Thirteen 21-day-old Wistar rats were made unilaterally cryptorchid by closing the left inguinal canal. At day 30 (Group 1, n=6) and day 60 (Group 2, n=7) after operation, the testes were removed for histopathological examination. The controls (n=8) were sham operated and were sacrificed at day 60. Germ cell apoptosis was assessed by means of the TUNEL method. Results: Spermatogenesis was arrested and the testicular and seminiferous tubular diameters were significantly reduced In the unilateral undescended testes (UUTs) compared with the contralateral descended testes (CDTs) and the control rats. However, atrophic changes, pathological calcification, necrosis of seminiferous tubule, and absence or sloughing of germ cells were not found in all the animals. The spermatocytes were the main type of germ cells undergoing apoptosis in all the groups. In the UUTs, there was a significant and time-depe     

Protective effects of royal jelly on testicular torsion induced ischaemia reperfusion injury in rats

This study was performed to investigate the protective effects of royal jelly (RJ) on a testicular torsion-induced ischaemia/reperfusion (I/R) injury in adult rats. A total of 40 male Wistar rats were divided into four groups, including 10 rats in each group: Group 1 (sham), Group 2 (Control), group 3 (I/R rats treated with 100 mg/kg RJ for 50 days after torsion) and group 4( I/R rats treated with 20 mg/kg vitamin C for 50 days after torsion). Testicular torsion was created by rotating the right testes 720° a clockwise direction for 90 min. The levels of testosterone were measured by ELISA. Pathological evaluation, mean maturity and quality of the seminiferous tubules were used. Results showed that the testicular histopathology standards and testosterone levels changes were statistically significant in groups 3 and 4. The results obtained in this study may suggest that RJ like vitamin C had protective effects on a testicular ischaemia/reperfusion-induced injury in rats.     

Effect of nicotine on spermatogenesis in adult albino rats

This study aimed to assess the effects of nicotine on spermatogenesis in 140 mature male albino rats divided into group A (controls), group B (sham controls), group C (nicotine treated) and group D (nicotine withdrawal). Group C was subdivided into CI, CII, CIII according to the dose of injected nicotine (0.2, 0.4 and 0.6 mg nicotine per 100 g per day), where each subgroup was further subdivided according to the treatment duration into subgroups a, b and c that received nicotine for 2, 4 and 8 weeks. Group D received nicotine for 8 weeks followed by withdrawal for another 8 weeks to assess testicular recovery. Testicular tissue sections were subjected to haematoxylin and eosin, Masson's trichrome stains and morphometry. The results showed that nicotine caused degenerative changes in the seminiferous tubules, revealed by altered general tubular architecture, decreased thickness of the spermatogenic cell masses, Sertoli cell vacuolation and thickened basal lamina. These changes were proportional to the nicotine dose and duration. Following nicotine withdrawal, regeneration of the damaged seminiferous tubules was observed to be rather complete in CI group. It is concluded that nicotine could adversely affect testicular spermatogenesis in a dose- and time-dependent manner which would be almost reversible after nicotine withdrawal, especially after small doses.     

Human chorionic gonadotropin deteriorates the histology of rat testes

OBJECTIVES: It is not yet certain whether early hormonal treatment in cryptorchidism is safe for germ cells. We investigated the histologic effects of human chorionic gonadotropin (hCG) therapy on descended testes of rats. DESIGN AND SETTING: Thirty male Wistar albino rats were randomized into two groups. The rats of the hCG group (n=15) were administered 50 IU/kg/day hCG once daily via the subcutaneous route for 15 days. Fifteen rats received subcutaneous isotonic saline and acted as controls. At the first month, testicular tissue was obtained after scarification in both groups. The histological examination was performed to evaluate the seminiferous tubular diameter, germinal membrane thickness, and the percentage of the open seminiferous tubule lumen in each testis to compare the two groups. RESULTS: The percentage of the open seminiferous tubular lumen in testicular tissues of hCG-treated rats was higher than that of controls (p<0.05). The mean germinal membrane thickness in testicular tissues of the hCG group was statistically lower than that of the control group (p<0.05). There was no statistical difference between mean seminiferous tubular diameter in testicular tissues of hCG-treated rats and controls, as expected (p>0.05). Additionally, there were two interesting cases of Sertoli cell only appearance in the hCG group. CONCLUSIONS: We may assume that hCG impairs the seminiferous tubule histology in normal testes of rats. Thus, further experimental studies on dose dependency and the reversibility of these effects are warranted.     

Cisplatin-induced germ cell apoptosis in mouse testes

The purpose of this study was to investigate whether exposure of male mice to cisplatin induces apoptosis in male germ cells and the possible role of apoptosis in cisplatin-induced testicular damage. Forty-eight male BALB/c mice were divided into cisplatin and control groups. The mice from the cisplatin group received a single intraperitoneal injection of cisplatin of either 1, 5, or 10 mg/kg. The control group received a single intraperitoneal injection of saline alone. The testes were removed on days 1, 3, and 7 after cisplatin administration, respectively. Following histological examination, apoptotic indices (AIs) were measured within seminiferous tubules of the mouse testes by terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling assay. A low incidence of spontaneous apoptosis was observed in controls, particularly in spermatogonia and spermatocytes of the mouse testes. After cisplatin administration, both increased Als and decreased spermatozoa and spermatids were found in the seminiferous tubules of the mouse testes. Cisplatin-induced apoptosis was found in spermatogonia, spermatocytes, and spermatids of the mouse testes. In comparison to the control values, AIs increased 2.6- to 6.8-fold in cisplatin-treated mouse testes. AIs reached the highest level on day 1 following 1 mg/ kg, on day 3 following 5 mg/kg, and on day 7 following treatment of 10 mg/kg cisplatin. The study showed that cisplatin-induced germ cell apoptosis in the mouse testes was related to both the dose response and the time course of response. It is suggested that cisplatin-induced germ cell apoptosis may result in decreased spermatogenesis, and the higher dose of cisplatin may delay the occurrence of apoptosis in the mouse testes.     

The protective effects of nitric oxide on the contralateral testis in prepubertal rats with unilateral testicular torsion

OBJECTIVE: To investigate histological changes in the contralateral testis of rats with unilateral testicular torsion and the protective effects of nitric oxide (NO) on possible damage. MATERIAL AND METHODS: Twenty-eight prepubertal male Sprague-Dawley rats were divided into four equal groups. Group 1 underwent a sham operation of the right testis under general anaesthesia. Group 2 underwent a similar operation but the right testis was rotated 720 degrees clockwise for 6 h, maintained by fixing the testis to the scrotum, and saline infused during the procedure. Group 3 underwent similar torsion but L-arginine methyl ester (a precursor of NO) was infused during the procedure. In Group 4, NG-nitro-L-arginine-methyl ester, a NO synthase inhibitor, was infused separately during the administration of L-arginine methyl ester and torsion. All the left (untwisted) testes were removed from rats 21 days after surgery and evaluated histologically, assessing seminiferous tubule diameter, loss of sperm and spermatids, loss of germ cell layers, disarray of germ cell layers, rupture of tubules, Leydig cell proliferation and reaction in the ruptured tubules, and oedema. RESULTS: There was a significant difference in the indicators of histological damage between groups 2 and 4 and groups 1 and 3, except for the Leydig cell reaction in the ruptured tubules and oedema. The damage was significantly less in group 3 than in groups 2 and 4. CONCLUSION: These results suggest that long-term histopathological changes in the contralateral testes are important after unilateral testicular torsion and that NO has a protective effect on the contralateral testis.     

Gossypol with methyltestosterone and ethinylestradiol male does not affect rat spermatogonial stem cell differentiation

The purpose of this study was to investigate whether administration of the regimen of gossypol at 12 mg/kg/day combined with methyltestosterone at 20 mg/kg/day and ethinylestradiol at 100 microg/kg/day for a long term of twenty-four weeks could affect the existence and differentiation of rat spermatogonial stem cell. This was assessed by conducting TdT-mediated dUTP nick end-labeling detection, spermatogonial stem cell transplantation and fertility recovery evaluation. Our results showed that spontaneous apoptosis was observed in normal rats' testes from the control group with an apoptotic index (AI) average of 10.24+/-1.52. In the regimen-treated group, the predominant apoptotic cells were spermatocytes and spermatids in the seminiferous tubules. Spermatogonia were not apoptotic (AI averaged 113.42+/-13.24). Two to three months after transplantation of spermatogonial stem cells isolated from regimen-treated rats into recipient nude mice, elongated rat spermatids were identified in the seminiferous tubules of recipient nude mice. Six weeks after withdrawal of the administration, fertility of the regimen-treated rats was recovered compared with that of the control group. The number of litters produced by females mated with regimen-treated males averaged 9.88+/-0.166 matched 10.30+/-0.171 of control group and the litters of the first generation appeared to be normal. These results indicated that the administration of this regimen did not affect the existence and differentiation potential of spermatogonial stem cells of the regimen-treated rats.     

Effect of ultrasound on testicular electrolytes (sodium and potassium).

The testes of 50 rats were placed in a cup filled with water and received 1 W/cm2 of ultrasound for 15 min. Fluid was collected from the seminiferous tubules and rete testis of the treated and control groups at 1, 8, 12, and 24 hr intervals. Ultrasound increased the sodium concentration in the fluid of the seminiferous tubules, decreased the sodium concentration in the fluid of the rete testis, increased the potassium concentration in the fluid of the rete testis, and decreased the potassium concentration in the fluid of the seminiferous tubules. Fourteen, slightly sedated, monkeys (Macaca fascicularis) were treated with 1/2 W/cm2 of ultrasound for 30 min. Water was used as the coupling agent for seven monkeys and 3% NaCl was used as the coupling agent for the other seven monkeys. The efficacy of ultrasound treatment in reducing sperm count to zero and achieving zero motility was increased when 3% NaCl was used. Sperm count was at the level of presonication after 20 weeks when water was used as a coupling agent.     

Immunohistochemical localization of enkephalinlike peptides during testicular development in rats

The distribution of opioid peptides is of interest in the rat testes, because the presence of opiate binding sites strongly supports the hypothesis of paracrine function for these peptidergic factors. Testes of Wistar albino rats between birth and adult stage were examined immunocytochemically for enkephalins, dynorphin, and alpha neoendorphin. The presence of immunoreactive enkephalinlike substances was visualized in both interstitial tissue and seminiferous tubules, but no staining was observed for dynorphin or neoendorphin. In interstitial tissue the material stained in Leydig cells raised after birth, declined at day 12, and increased again between day 22 and day 35 of life. From day 35 till adult stage we observed again a slight decrease of immunostaining. In seminiferous tubules, intense immunostaining was observed in stem spermatogonia until day 7 of life. After this period the presence of immunoreactive enkephalinlike material was detected, mainly in some spermatogonia and peritubular primary spermatocytes. These data suggest a possible implication of enkephalinlike peptides in spermatogonesis.