Development of stage-specific paracrine regulation of Leydig cells by the seminiferous tubules

The size of peritubular Leydig cells surrounding tubules in different stages of the spermatogenic cycle was determined in 43- and 47-day-old male rats. A stage-dependent variation in the size of peritubular Leydig cells was not present in 43-day-old rats, but by 47 days those Leydig cells closely adjacent to tubules at stages VII-VIII were larger than others. At 43 days of age spermatogenesis had developed up to step 18 spermatids in late stage VI tubules. At 47 days of age the first mature sperm had just been released from the seminiferous epithelium, and consequently the first wave of the spermatogenic cycle was completed. Tubules at stages VII-VIII therefore acquire the ability to influence surrounding Leydig cells when they contain step 19 spermatids. It remains to be shown whether this maturation step is due to inherent maturation of the Sertoli cells or if step 19 spermatids specifically modulate Sertoli cell function.     

Paracrine regulation of Leydig cells by the seminiferous tubules

Testes of adult control and unilateral cryptorchid rats were fixed by vascular perfusion. The cell profile area of peritubular Leydig cells surrounding tubules in different stages of spermatogenesis, and the cell profile area of perivascular Leydig cells were determined. The size of peritubular Leydig cells was dependent on which type of tubulus the cells were surrounding. Some peritubular Leydig cells, especially those surrounding stages VII–VIII (88.1 ± 7.1 μm², mean ± SD, n = 6 rats), were larger than perivascular Leydig cells (69.3 ± 5.9 μm²). The size of Leydig cells surrounding stages IX–XIV was similar to that of perivascular cells. In the abdominal testes no spermatogenic cycle was present and the sizes of peritubular and perivascular Leydig cells were equal (63.0 ± 5.1, vs 66.7 ± 7.3 μm², mean ± SD, n = 5 rats). It is suggested that the tubules and the spermatogenic cycle locally modulate Leydig cell activity and that Leydig cell malfunction in abdominal testes may be due to a decreased stimulatory influence from the damaged tubules.     

The effect of selective destruction and regeneration of rat Leydig cells on the intratesticular distribution of testosterone and morphology of the seminiferous epithelium

This study was designed to explore the relationship between the intratesticular distribution of testosterone and spermatogenesis by completely destroying the Leydig cells of mature male rats with injection of a single i.p. dose of ethane dimethanesulphonate. After such treatment, testosterone levels in serum, testicular interstitial fluid, seminiferous tubules, and whole testis declined significantly 6 to 24 hours after injection and fell below assay detection limits between 3 and 7 days. At 3 and 7 days, serum LH and FSH levels rose significantly and remained elevated up to 4 and 6 weeks, respectively, in comparison with vehicle-treated controls. Leydig cells disappeared from the interstitium by day 3, but between 2 and 4 weeks postinjection a new generation of fetal-like Leydig cells repopulated the testicular interstitium and, during weeks 6 to 10, were transformed into, or replaced by, Leydig cells with an adult type of morphology. Histologic examination of the seminiferous tubules showed progressive disruption of spermatogenesis between 3 and 14 days post-ethane dimethanesulphonate. The first histologic sign of spermatogenic damage was noted at day 3, with the occurrence of stage-specific degenerating pachytene primary spermatocytes at stages VII to VIII of the spermatogenic cycle. On day 7, these cells and degenerating round, or step 19, spermatids often were observed during stages VII to XI, although qualitatively normal spermatogenesis also was seen in these and all other stages of the cycle. Maximum impairment of spermatogenesis occurred 2 weeks post-ethane dimethane sulphonate, at which time the tubules commonly lacked one or more germ cell generations or, alternatively, showed accumulation of lipid inclusions, extracellular spaces, and variable numbers of degenerating germ cells. Following repopulation of the testis by Leydig cells during weeks 3 and 4, spermatogenesis recovered. By 10 weeks after treatment, qualitatively normal spermatogenesis was seen in the great majority of seminiferous tubules, although a few tubules still remained in which the germ cell complement was severely reduced, and contained only Sertoli cells and spermatogonia.(ABSTRACT TRUNCATED AT 400 WORDS)     

Evolution of somatic and germ cell populations after busulfan treatment in utero or neonatal cryptorchidism in the rat

Summary.  In order to elucidate the respective effects of depletion of germ cells and of increase in testicular temperature, rats of the same Wistar strain were rendered experimentally bicryptorchid or sterilized by a busulfan injection in utero and compared to control animals. In both models, germ cells were depleted but numeric evolution and functions of somatic cells differed. The aim of that work was to compare the numeric evolutions of testicular somatic and germ cells to their respective functions in each model before puberty and in adult rats of the same strain. Serum concentrations of FSH, LH and testosterone were compared at 20, 40 and 110 days of age. Histological analyses of Sertoli and germ cells in the seminiferous tubules and of Leydig cells in the intertubular tissue were performed before puberty and at adulthood. Testosterone serum concentrations were depleted in both models starting at 40 days of age and more in busulfan-treated rats. Both FSH and LH levels were increased from 20 days onwards in experimental rats. Additional cryptorchidism in busulfan-treated rats depressed the serum testosterone concentration. At 17 days of age, the cryptorchidism do not modify somatic or germ cell populations while busulfan treatment has induced a decrease of both these populations. Conversely, the cross sectional area of the somatic testicular cells was not affected whatever the treatment. In adult testes of busulfan-treated and cryptorchid rats, the total numbers of Sertoli and Leydig cells and of germ cells per testis were decreased. The cellular size of the perivascular Leydig cells was not modified by any of the treatments whereas the size of the Sertoli cells was reduced.
In conclusion, in both models the absence of germ cells induces a decrease in Sertoli cell function, while the increase in testicular temperature provokes degeneracies of Sertoli and germ cells in the seminiferous tubules of the rat.     

睾丸细胞生物学研究进展

睾丸是男性生殖腺,由生精小管和间质构成。生精小管主要由生精细胞和支持细胞组成,是精子发生场所;间质中主要是间质细胞,间质细胞合成与分泌雄激素。本文介绍睾丸3种细胞的发育分化,以及成年期睾丸细胞的结构和生物学研究进展。     

Testicular Biopsy and Hormonal Study in a Male with Noonan''s Syndrome

The testicular biopsy study of a 17-year-old male with Noonan's syndrome revealed seminiferous tubules of reduced diameter with hypospermatogenesis. Many spermatocytes underwent degeneration and many spermatids developed abnormal. The Sertoli cells were similar to immature Sertoli cells. Fully differentiated Leydig cells were rare while precursor Leydig cells were numerous. Both gonadotropin and testosterone levels were low, and a lack of response to LH-RH as well as to clomiphene was found. The testicular biopsy performed at 20 years of age revealed a certain maturation of the seminiferous tubules which increased the germ cell number. The abnormalities in the spermatogenesis as well as the immature appearance of Sertoli cells continued. Leydig cells were more numerous and showed a certain development without reaching the normal pattern. Gonadotropin levels were normal while testosterone levels low. The response to LH-RH was increased and the absence of response to clomiphene persisted. These features suggest a delayed puberty.     

Leydig cell hyperplasia in cryptorchid patients: Quantitative evaluation of Leydig cells in undescended and contralateral scrotal testes

Summary Leydig cell number was evaluated quantitatively in testicular biopsies from post-pubertal cryptorchid patients and normal controls. For this quantitative evaluation we used the following method. This is based on the determination of the total number of Leydig cells, Leydig cell clusters and seminiferous tubules in the entire histologic sections of each biopsy and the determination of the following indices; mean Leydig cells per tubule, mean Leydig cell clusters per tubule and mean Leydig cells per cluster. In addition, the numbers of Sertoli cells were counted, and Leydig-Sertoli cell ratio was also determined. These indices were correlated with each other. All indices were significantly elevated not only in undescended but in contralateral scrotal testes of the cryptorchid patients in comparison to those in normal controls. Between undescended and descended scrotal testes of the same individual patients, those indices were significantly higher in the descended scrotal testes than in the undescended ones. Thus, Leydig cell hyperplasia was noted in the testes of post-pubertal cryptorchid patients, and was more prominent in the contralateral scrotal testes than in the undescended ones.     

Êxpression of inducible nitric oxide synthase (iNOS) in the azoospermic human testis

Azoospermia, which is the absence of spermatozoa in the ejaculate, is not a rare cause of male infertility. Inducible nitric oxide synthase (iNOS) is a calcium-independent NOS, which is present in the testis and involved in spermatogenesis, and apoptosis of Sertoli and germ cells. Twenty idiopathic infertile men presenting nonobstructive azoospermia were enrolled in this study, and testicular sperm extraction procedures were performed. Tissue extracts were dissected, and the fluid samples were investigated to determine the presence of spermatozoa. Histologic evaluation of the spermatozoa-present samples revealed that seminiferous tubules were normal and were lined by Sertoli cells and spermatogenic cells. However, in the spermatozoa-absent samples, the diameter of the seminiferous tubules was small, and Sertoli-cell-only syndrome was determined in most of the tubules. iNOS expression was very weak in Sertoli cells, germ cells, and in Leydig cells in the spermatozoa-present group. In the spermatozoa-absent group, the immunostaining was very intense in Sertoli and Leydig cells. Electron microscopy findings were supported the histologic results. In conclusion, complete germ cell loss and intense expression of iNOS in the Sertoli and Leydig cells in the spermatozoa-absent groups of azoospermic human testis suggest an essential role of iNOS in spermatogenesis.     

Testosterone and spermatogenesis. Identification of stage-specific, androgen-regulated proteins secreted by adult rat seminiferous tubules.

The aim of this study was to identify potential androgen-regulated proteins (ARP) that might mediate the supportive effects of testosterone on spermatogenesis. Adult rats were injected with ethane dimethane sulphonate (EDS) to destroy Leydig cells and thus induce complete testosterone withdrawal. Other EDS-treated rats were injected with 25 mg testosterone esters (TE) every 3 days to maintain quantitatively normal spermatogenesis. A timeframe for the study of androgen action on spermatogenesis was deduced from enumeration of degenerating germ cells at stage VII of the spermatogenic cycle in perfusion-fixed testes from rats in the early stages (4 to 8 days) after EDS treatment. Based on this data and changes in testicular interstitial fluid volume, long seminiferous tubule segments were isolated from control rats and from EDS-treated rats (+/- TE-supplementation) at stages II-V, VI-VIII, or IX-XII, 2 days to 6 days after EDS treatment. Seminiferous tubule segments were incubated for 22 hours with 60 microCi 35S-labelled methionine. Incorporation into newly synthesized proteins in the seminiferous tubule culture medium (= secreted proteins) or in seminiferous tubule lysates (= intracellular proteins) was determined by trichloroacetic acid-precipitation followed by analysis using two-dimensional sodium dodecylsulfate polyacrylamide gel electrophoresis. In control rats, incorporation of 35S-methionine into proteins secreted by isolated seminiferous tubules was more than twice as great at stages VI-VIII than at stages II-V or IX-XII. This doubling in methionine incorporation into stages VI-VIII secreted proteins was abolished, however, 4 days after EDS treatment (when germ cell degeneration at stage VII was only just evident). A similar change occurred 4 days after testosterone withdrawal induced by immunoneutralization of luteinizing hormone. In the latter case and after EDS treatment, TE-supplementation of rats from day 0 maintained the normal control pattern of methionine incorporation into seminiferous tubule secreted proteins, although 6 days after EDS and TE treatment, incorporation into stages VI-VIII secreted proteins was 19% lower (P less than 0.05) than in the control group. In contrast, incorporation of methionine into proteins secreted by seminiferous tubules at stages II-V and IX-XII was unaffected by EDS and TE pretreatment, as was incorporation into intracellular proteins at all stages.(ABSTRACT TRUNCATED AT 400 WORDS)     

一氧化氮合酶同功异构酶在大鼠睾丸中的表达和定位

目的 :了解一氧化氮 ( NO)在睾丸中的作用。方法 :运用免疫组织化学方法观察 3种一氧化氮合酶 ( NOS)同功异构酶在大鼠生后 4、7、1 4、3 0、60 d睾丸中的分布。结果 :( 1 )生后 4、7、1 4d大鼠睾丸未见 3种 NOS免疫阳性反应 ;( 2 )生后 3 0 d少数精母细胞及生后 60 d生精小管腔面精子和间质细胞呈 NOS1阳性 ;( 3 )生后 3 0 d少数精母细胞、支持细胞和管周类肌细胞呈 NOS2阳性 ,而生后 60 d NOS2阳性反应见于睾丸间质细胞、管周类肌细胞、支持细胞、极少数精母细胞和不成熟精子头部 ;( 4)生后 3 0 d睾丸内少数精母细胞和血管壁呈 NOS3阳性 ,生后 60 d NOS3阳性反应仅见于血管壁。结论 :NO可能参与精子发生、睾酮的分泌过程 ,并调节睾丸内的血流。     

True hermaphroditism with bilateral ovotestis: a case report

A true hermaphrodite with a 46 XX/47 XXY karyotype, gynaecomastia, hypospadia and scrotal gonads was investigated. Gonadectomy performed at 14 years of age revealed bilateral ovotestes. The ovarian portion contained follicles of all developmental stages. The testicular portion was immature consisting of seminiferous cords with Sertoli cells at various steps of differentiation and few germ cells within massive aggregates of collagenous connective tissue. Leydig cells as well as germ cells remained in an embryonic stage of development. Sections of a differentiated Wolffian duct (ductuli efferentes, epididymis, vas deferens) as well as of a Müllerian duct (hypoplastic fallopian tube) were found adjacent to both gonads. Postoperative treatment consisted of androgen substitution therapy leading to progression of puberty.     

Developmental and stage-specific expression of Smad2 and Smad3 in rat testis

Members of the transforming growth factor beta type (TGFbeta) superfamily and their receptors are expressed in the testis, and are believed to play important paracrine and autocrine roles during testicular development and spermatogenesis. The Smad proteins are downstream mediators for the family of TGFbeta growth factors. Smad2 and Smad3 are associated with both TGFbeta and activin signaling. However, very little is known about the expression and regulation of the Smad signaling proteins in the testis. In the present study, we have determined that Smad2 and Smad3 proteins are expressed in the postnatal testes of rats from 5 days to 60 days of age. Expression levels for both proteins are higher in young rats than in sexually mature rats. Smad2 and Smad3 messenger RNA levels parallel protein expression. Smad2 and Smad3 proteins are mainly localized in the cytoplasm of meiotic germ cells, Sertoli cells, and Leydig cells. Smad3 protein is localized to the nucleus of preleptotene to zygotene primary spermatocytes in young rats. Both proteins are expressed throughout all stages of the cycle of seminiferous tubules but are expressed at their lowest levels at stages VII-VIII in the seminiferous epithelium of adult rats. The presence of these downstream mediators in these cell types supports a role for TGFbeta and activin during spermatogenesis. The difference between the expression of Smad2 and Smad3 suggests that they may have different functions within the testis.     

Ontogeny and cellular origin of a rat seminiferous tubule factor(s) that inhibits LH-dependent testosterone production by interstitial cells in vitro

Previous studies have shown the presence of a peptide in spent media from incubated seminiferous tubules (SMST), which inhibits LH stimulation of testosterone production by rat Leydig cells in vitro. The present study has investigated whether the secretion of this inhibitor changes during development in the rat. Seminiferous tubules obtained from rats aged 10, 20, 25, 30, 35, 40, 42, 50 or 60 days were incubated at 32 degrees C for 24 h. Spent media from these incubations were then added to interstitial cells isolated from the testes of rats aged 60 days. Spent media from rats aged 10-30 days had no effect on basal or oLH-stimulated testosterone production by interstitial cells during 3-h incubation. Significant inhibition of LH-stimulated testosterone production was, however, observed with SMST from rats aged 35-60 days. Spent media prepared using tubules from normal, prenatally irradiated (Sertoli cell-enriched) or seminiferous tubules, depleted of peritubular cells, had no effect on basal, but inhibited LH-stimulated, testosterone production. Spent media from peritubular cell cultures had no effect on basal or LH-stimulated testosterone production by interstitial cells. The inhibitory effect of SMST was also dependent on the age of the rats providing the target cells. Interstitial cells from rats aged 10, 20, 50 or 60 days were responsive to the inhibitor while cells from rats aged 30 and 40 days were not. The results of the present study demonstrate that the seminiferous tubule factor(s), which inhibits LH action on interstitial cells, is first secreted at 35 days, a time when the most mature germ cells present are in the early maturation phase. Moreover, interstitial cells are responsive to this factor in both immature (10-20 day-old) and mature (50-60 day-old) rats, but not at ages in between these times. It is suggested that the adult Sertoli cell is the major source of the interstitial cell inhibitor.     

Expression of endothelial nitric oxide synthase in the Sertoli cells of men with infertility of various causes

OBJECTIVE: To investigate how endothelial nitric oxide (eNOS) expression in the seminiferous tubules might be related to spermatogenesis, by examining eNOS expression in testicular tissue of patients infertile from various causes. PATIENTS AND METHODS: The study included five fertile men with a normal sperm concentration, nine patients with obstructive azoospermia, 20 with varicocele testes and eight with idiopathic azoospermia (Sertoli cell-only syndrome). Testicular biopsy specimens were examined by immunohistochemistry for eNOS protein expression, in addition to a routine pathological assessment. eNOS protein was detected using an eNOS monoclonal antibody. A Sertoli cell staining index (SSI) was defined as the ratio of stained Sertoli cells per total number of Sertoli cells, and was compared among the groups. RESULTS: eNOS was localized to Sertoli cells in the seminiferous tubules and Leydig cells in the interstium; although some degenerating germ cells stained, normal germ cells did not. The SSI was significantly lower in patients with Sertoli cell-only syndrome than in either fertile men or patients with obstructive azoospermia or varicocele. However, the SSI did not correlate significantly with the Johnsen score. CONCLUSION: The expression of eNOS in Sertoli cells may depend on the existence of germ cells and be associated with germ cell development.     

抑制素B βB亚单位在不同病理分型的无精子症患者睾丸组织中的表达

目的:探讨抑制素B(INH B)βB亚单位在不同生精功能状态的人睾丸组织中的表达情况。方法:对83例无精子症患者进行睾丸组织病理检查诊断,根据病理形态的不同分为:唯支持细胞综合征型(n=21);生精功能低下型(n=20);生精阻滞型(n=24);生精功能基本正常型(n=18)。选择上述各型结构完整的睾丸组织,分别应用免疫组化法(SP)对血清INH B βB亚单位在不同生精功能状态的睾丸组织,进行定位研究。结果:各型睾丸组织内均存在血清INH B βB的表达,其分布特点为:间质细胞(Leydig cell)和早期生精细胞多为强阳性表达,呈深棕黄色;支持细胞(Sertoli cell)多为阳性表达;而晚期精子细胞和成熟精子未见表达;生精小管管周类肌细胞呈弱阳性表达。结论:INH B可能是睾丸Sertoli细胞和早期生精细胞的一个联合产物。     

Spermatogenese

Spermatogenesis takes place within the testicular seminiferous tubules which consist of the peritubular lamina propria and the seminiferous epithelium. The latter is composed of germ cells and somatic Sertoli cells. Sertoli cells trigger germ cell development by mediating follicle-stimulating hormone and androgen hormonal stimuli. Spermatogenesis comprises proliferation of spermatogonia, meiosis of spermatocytes, and differentiation of spermatids into spermatozoa (spermiogenesis). There are six distinct and specific germ cell associations (I–VI). These “stages of spermatogenesis” occur sequentially along the length of a tubule. Different defects in spermatogenesis occur in adjacent seminiferous tubules (mixed atrophy) and are associated with deficits in differentiation of Sertoli cells. Biopsy specimens should be fixed in Bouin’s solution. Diagnosis of preinvasive carcinoma in situ is based on the immunohistochemical demonstration of placental-like alkaline phosphatase (PLAP), which is expressed exclusively in carcinoma in situ cells. Histological evaluation should be performed using a score count system, and the use of histological techniques for protein and mRNA expression. Testicular biopsy should only be performed in accordance with strict indication criteria, and histological evaluation should be carried out in specialist centres, i.e. as recommended by the European Academy of Andrology (EAA).     

Spermatogenesis--physiology and pathophysiology

Spermatogenesis takes place within the testicular seminiferous tubules which consist of the peritubular lamina propria and the seminiferous epithelium. The latter is composed of germ cells and somatic Sertoli cells. Sertoli cells trigger germ cell development by mediating follicle-stimulating hormone and androgen hormonal stimuli.Spermatogenesis comprises proliferation of spermatogonia, meiosis of spermatocytes, and differentiation of spermatids into spermatozoa (spermiogenesis). There are six distinct and specific germ cell associations (I-VI). These "stages of spermatogenesis" occur sequentially along the length of a tubule. Different defects in spermatogenesis occur in adjacent seminiferous tubules (mixed atrophy) and are associated with deficits in differentiation of Sertoli cells. Biopsy specimens should be fixed in Bouin's solution. Diagnosis of preinvasive carcinoma in situ is based on the immunohistochemical demonstration of placental-like alkaline phosphatase (PLAP), which is expressed exclusively in carcinoma in situ cells. Histological evaluation should be performed using a score count system, and the use of histological techniques for protein and mRNA expression. Testicular biopsy should only be performed in accordance with strict indication criteria, and histological evaluation should be carried out in specialist centres, i.e. as recommended by the European Academy of Andrology (EAA).     

Morphological alterations and intratubular lipid inclusions as indicative of spermatogenic damage in cimetidine-treated rats

Doses of cimetidine (50 mg/kg b/w) were administered to adult male Wistar rats over 52 consecutive days. Besides plasma testosterone levels, morphological and morphometric aspects of the seminiferous tubules as well as histochemical analysis of the lipid content by oil red O were emphasized. Abnormal tubules exhibiting disorganization of their cellular association, loss of germ cells, and multinucleated giant spermatids were usually found. Significant reductions of testis weight and tubular diameter at specific stages (VII-IX), as well as lack of contact between Sertoli cells and spermatids in tubules at stage IX, suggest a possible interference of cimetidine on the histoarchitecture of the seminiferous epithelium. The dense concentration of lipid inclusions in tubules at postspermiation stages indicates phagocytosis and degradation of germ cells. Since no change in serum testosterone levels was verified in cimetidine-treated rats, the authors could not exclude the possibility that besides an antiandrogenic effect, other biochemical factors necessary for normal spermatogenesis could be involved in the testicular alterations.     

The selective removal of pachytene spermatocytes using methoxy acetic acid as an approach to the study in vivo of paracrine interactions in the testis

Testicular weight and morphology, serum gonadotropins, intratesticular levels of testosterone and ABP levels in testicular interstitial fluid were studied in adult rats at intervals of 1 to 70 days after a single oral dose of 650 mg/kg methoxy acetic acid. At 3 days, this treatment resulted in the selective loss or depletion of pachytene and later spermatocytes from seminiferous tubules at all stages other than VIII to XI of the spermatogenic cycle. At later times this lesion was expressed as an absence mainly of round (14 days) or elongated (21 days) spermatids from the majority of seminiferous tubules. Other than these changes, spermatogenesis did not appear to be affected by treatment and was qualitatively normal in all tubules at 70 days after treatment. As deduced from cell counts at 3 days posttreatment, the initial action of methoxy acetic acid was restricted to late zygotene spermatocytes (stage XII) and pachytene spermatocytes at all stages other than early- to mid-stage VII. Levels of FSH in serum and those of ABP in testicular interstitial fluid indicated that Sertoli cell function was altered in rats treated with methoxy acetic acid. Both were increased at 1 to 3 days posttreatment, returned to normal at 7 to 14 days but were increased again at 21 days before finally returning to control levels at 28 days. In contrast, the levels of testosterone in serum, isolated seminiferous tubules and testicular interstitial fluid were unaffected by treatment, as also were the serum levels of LH. The two periods of increase in FSH and ABP levels coincided with the times of greatest decrease (approximately 20%) in testicular weight, and may be related either to the type of germ cell missing from the affected tubules and/or to the stage of the cycle of the affected (or unaffected) tubules. These data suggest that chemicals such as methoxy acetic acid may prove useful in the study of paracrine interactions in vivo.     

Spermatogenic cycle length and spermatogenic efficiency in the gerbil (Meriones unguiculatus)

The gerbil (Meriones unguiculatus) is a rodent native of the arid regions of Mongolia and China. Because the gerbil can be easily bred in laboratory conditions, this species has been largely used as an experimental model in biomedical research. However, there is still little information concerning the testis structure and function in the gerbil. In this regard, we performed a detailed morpho-functional analysis of the gerbil testis and estimated the spermatogenic cycle length utilizing 3H-thymidine as a marker for germ cell progression during their evolution through the spermatogenic process. The stage frequencies of the XII stages characterized according to the acrosome formation and development were (I-XII) 13.8, 10.1, 8.1, 7.8, 4.0, 11.2, 7.5, 7.1, 5.9, 7.6, 8.1, and 8.9. The mean duration of each seminiferous epithelium cycle was determined to be 10.6 +/- 1.0 days and the total duration of spermatogenesis, based on 4.5 cycles, was approximately 47.5 days. The volume density of tubular and interstitial compartments was approximately 92% and 8%, respectively. Based on the volume occupied by seminiferous tubules in the testis and the tubular diameter, about 9 and 18 m of seminiferous tubules were found per testis and per gram of testis, respectively. Twelve primary spermatocytes were formed from each type A1 spermatogonia. The meiotic index was 2.8, indicating that 30% of cell loss occurs during meiosis. The number of Leydig and Sertoli cells per gram of the testis was 28 million and each Sertoli cell was able to support approximately 13 spermatids. The daily sperm production per gram of testis (spermatogenic efficiency) was 33 million. Taken together, these data indicate that, mainly due to the high seminiferous tubule volume density and Sertoli cell support capacity for germ cells, the gerbil presents high spermatogenic efficiency compared with other mammalian species already investigated. The data obtained in the present study might provide the basis for future research involving the reproductive biology in this species.