Dose and time relationships in the endocrine response of the irradiated adult rat testis

Effects of Continuous In Utero Low- and Medium-Dose-Rate Gamma-Ray Exposure on Fetal Germ Cells

The effects of radiation exposure on germ cells and the gonads have been well studied at acute high-dose exposures, but the effects of chronic low-dose-rate (LDR) irradiation, particularly relevant for radiation protection, on germ cells and the gonads are largely unknown. Our previous study revealed that chronic exposure of mice to medium-dose-rate (MDR, 200 or 400 mGy/day) gamma-rays in utero for the entire gestation period (18 days) induced only a mild degree of general growth retardation, but with very drastic effects on the gonads and germ cells. In the current study, we further investigated the histomorphological changes in the gonads and the number of germ cells from gestation day (GD) 18 fetuses irradiated with MDR throughout the entire gestation period. The germ cells in the testes and ovaries of the MDR-irradiated fetuses were almost obliterated. Gestation day 18 fetuses exposed to LDR (20 mGy/day) radiation for the entire gestation period showed decreases in the number of the germ cells, which were not statistically significant or only marginally significant at most. Further investigations on the effects of LDR irradiation in utero using more sensitive methods are necessary.

Cryptorchidism after the Fukushima Daiichi Nuclear Power Plant accident:causation or coincidence?

Cryptorchidism (undescended testes) is among the most common congenital diseases in male children. Although many factors have been linked to the incidence of cryptorchidism, and testicular androgen plays a key role in its pathogenesis, the cause remains unknown in most cases. Recently, a Japanese group published a speculative paper entitled, "Nationwide increase in cryptorchidism after the Fukushima nuclear accident." Although the authors implicated radionuclides emitted from the Fukushima accident as contributing to an increased incidence of cryptorchidism, they failed to establish biological plausibility for their hypothesis, and glossed over an abundance of evidence and expert opinion to the contrary. We assessed the adequacy of their study in terms of design setting, data analysis, and its conclusion from various perspectives. Numerous factors must be considered, including genetic, environmental, maternal/fetal, and social factors associated with the reporting of cryptorchidism. Other investigators have established that the doses of external and internal radiation exposure in both Fukushima prefecture and the whole of Japan after the accident are too low to affect testicular descent during fetal periods;thus, a putative association can be theoretically and empirically rejected. Alternative explanations exist for the reported estimates of increased cryptorchidism surgeries in the years following Japan's 2011 earthquake, tsunami, and nuclear crisis. Data from independent sources cast doubt on the extent to which cryptorchidism increased, if at all. In any case, evidence that radionuclides from the Fukushima Daiichi Nuclear Power Plant could cause cryptorchidism is lacking.

Post-irradiation protective effects of ectoine on brain and testicles in male mice

BACKGROUND

The present study aimed to investigate the possible post-irradiation protective effects of ectoine on CNS and testes of male mice.

METHODS

The study included thirty male Swiss albino mice (20-22 gm). Mice were divided into five groups (six each); controls (injected intraperitoneally with 0.2ml saline), irradiated group 1 (received six Gy whole body x-irradiation single dose, injected with saline, and sacrificed after one day), irradiated group 2 (x-irradiated, injected with saline, and sacrificed after one week), ectoine group 1 (x-irradiated, injected with 200mg/kg ectoine, and sacrificed after one day), and ectoine group 2 (x-irradiated, injected daily with 200mg/kg ectoine, and sacrificed after one week). IL-1β, IL-6, IL-10, PGE₂, MDA, GSH, GSSG, and GSH/GSSG ratio were evaluated in CNS and testes.

RESULTS

IL-1β, IL-6, IL-10, PGE₂, and MDA are significantly elevated in the CNS and testes of x-irradiated groups when compared with controls. IL-1β, IL-6, IL-10, and PGE₂ significantly elevated at one week than one day while MDA significantly decreased. A significant decrease in the concentration of GSH and in the GSH/GSSG ratios coupled with an opposite effect on GSSG was noted. Ectoine treatment significantly ameliorated the biochemical effects induced by whole body x-irradiation. All the tested parameters tended to go back to near control values. It was noted that the modulating action was dependent on the accumulation of ectoine as it was more effective after repeated administration.

CONCLUSION

Ectoine has post-irradiation protective effects on CNS and testes via its action on inflammatory and oxidative stress pathways.

Persistent testicular structural and functional alterations after exposure of adult rats to atrazine

Atrazine is an endocrine disruptor affecting testicular steroidogenesis, and promoting testicular atrophy and 3β-HSD reduction. However, it remains unknown whether these effects are reversible or permanent. To address this issue was the aim of this study. Exposition of rats to 200mg/kg of atrazine resulted in transient increase in testicular weight, seminiferous tubules dilation and atrophy, and reduction in Leydig cell 3β-HSD. Testicular atrophy and 3β-HSD reduction were more pronounced after the recovery period of 75days. There was increase in aromatase expression after long-term exposure but it returned to control level after recovery. Moreover, there was increase in ED1^-/ED2⁺, ED1⁺/ED2⁺ and ED1⁺/ED2^- macrophages, in the recovery group. These macrophages were positive for 3β-HSD, thereby raising possibility of their involvement in steroidogenesis. These findings further emphasize the adverse effects of atrazine on male reproduction, highlighting that testicular damages may be irreversible even after a recovery period longer than the spermatogenic cycle.

Leydig cells contribute to the inhibition of spermatogonial differentiation after irradiation of the rat

Irradiation with 6 Gy produces a complete block of spermatogonial differentiation in LBNF1 rats that would be permanent without treatment. Subsequent suppression of gonadotropins and testosterone (T) restores differentiation to the spermatocyte stage; however, this process requires 6 weeks. We evaluated the role of Leydig cells (LCs) in maintenance of the block in spermatogonial differentiation after exposure to radiation by specifically eliminating functional LCs with ethane dimethane sulfonate (EDS). EDS (but not another alkylating agent), given at 10 weeks after irradiation, induced spermatogonial differentiation in 24% of seminiferous tubules 2 weeks later. However, differentiation became blocked again at 4 weeks as LCs recovered. When EDS was followed by treatment with GnRH antagonist and flutamide, sustained spermatogonial differentiation was induced in >70% of tubules within 2 weeks. When EDS was followed by GnRH antagonist plus exogenous T, which also inhibits LC recovery but restores follicle stimulating hormone (FSH) levels, the spermatogonial differentiation was again rapid but transient. These results confirm that the factors that block spermatogonial differentiation are indirectly regulated by T, and probably FSH, and that adult and possibly immature LCs contribute to the production of such inhibitory factors. We tested whether insulin-like 3 (INSL3), a LC-produced protein whose expression correlated with the block in spermatogonial differentiation, was indeed responsible for the block by injecting synthetic INSL3 into the testes and knocking down its expression in vivo with siRNA. Neither treatment had any effect on spermatogonial differentiation. The Leydig cell products that contribute to the inhibition of spermatogonial differentiation in irradiated rats remain to be elucidated.

Ionizing radiation effects on sex steroid hormone levels in serum and milt of freshwater fish Oreochromis mossambicus

Effects of gamma rays on the sex steroid hormone levels [testosterone (T), 11-ketotestosterone (11-KT) and 17β-estradiol (E2)] were studied in the freshwater fish Oreochromis mossambicus. Gamma radiation induced effects on hormone levels reported here for the first time in the fish. Since radionuclides released accidentally or during a nuclear disaster can contaminate inland water bodies, biomonitoring methods are required for assessing the impacts of certain dose levels of radiation that may ultimately result in ionizing radiation exposure to both humans and non-human biota. Three groups of (n=15 in each group) fishes were irradiated with a single dose of (60)Co 10Gy, 15Gy and 20Gy with a duration of .33, .50 and .66min. Significant decrease of the hormone levels was seen at higher doses of 15Gy and 20Gy. The sex steroid hormone levels in the fishes are vital for sperm production, development, differential functions related to the physiology and reproductive behavior. This study serves as biomonitoring tool to assess the ionizing radiation effects on reproductive behavior of aquatic biota.

Rat models of post-irradiation recovery of spermatogenesis: interstrain differences

Recently, we reported large differences between rat strains in spermatogenesis recovery at 10 weeks after 5-Gy irradiation suggesting that there are interstrain as well as interspecies differences in testicular radiation response. To determine whether these interstrain differences in sensitivity might be a result of the particular dose and time-point chosen, we performed dose-response and time-course studies on sensitive Brown-Norway (BN) and more resistant spontaneously hypertensive rats (SHR) and Sprague-Dawley (SD) rats. Type A spermatogonia were observed in atrophic tubules at 10 weeks after irradiation in all strains indicating that tubular atrophy was caused by a block in their differentiation, but the doses to produce the block ranged from 4.0 Gy in BN to 10 Gy in SD rats. Although the numbers of type A spermatogonial were unaffected at doses below 6 Gy, higher doses reduced their number, indicating that stem cell killing also contributed to the failure of recovery. After 10 weeks, there was no further recovery and even a decline in spermatogonial differentiation in BN rats, but in SHR rats, sperm production returned to control levels by 20 weeks after 5.0 Gy and, after 7.5 Gy, differentiation resumed in 60% of tubules by 30 weeks. Suppression of testosterone and gonadotropins after irradiation restored production of differentiated cells in nearly all tubules in BN rats and in all tubules in SHR rats. Thus, the differences in recovery of spermatogenesis between strains were a result of both quantitative differences in their sensitivities to a radiation-induced, hormone-dependent block of spermatogonial differentiation and qualitative interstrain differences in the progression of post-irradiation recovery. The progression of recovery in SHR rats was similar to the prolonged delays in recovery of human spermatogenesis after cytotoxic agent exposure and thus may be a system for investigating a phenomenon also observed in men.

Donor Sertoli cells transplanted into irradiated rat testes stimulate partial recovery of endogenous spermatogenesis

Irradiation of rat testes leads to the failure to support differentiation of the surviving spermatogonia due to damage of the somatic environment. To determine the involvement of Sertoli cells in this somatic damage, we transplanted seminiferous tubule cells from normal immature GFP-transgenic rats into the testes of irradiated rats. The donor Sertoli cells colonized and developed in the host testes. In many seminiferous tubules, the donor Sertoli cells formed abnormal spherical structures in the lumen, but in some tubules they formed a normal-appearing epithelium, but with only isolated spermatogonia, on the basement membrane. When the donor cells were injected into the interstitial region of the testis, they formed tubule-like structures containing Sertoli cells and occasional isolated spermatogonia, both of donor origin. Surprisingly, in host tubules adjacent to these newly formed donor-cell tubules or adjacent to the endogenous tubules with abnormal donor Sertoli-cell structures, endogenous spermatogonia differentiated to the spermatocyte or even to spermatid stages. Around these newly donor cell-formed tubules and the host tubules with abnormal donor Sertoli-cell structures, many cells including macrophages, which perhaps represented chronic inflammation, accumulated in the interstitium. We conclude that the donor Sertoli cells that colonized the seminiferous tubules did not directly support recovery of spermatogenesis. Instead, the colonizing Sertoli cells acted indirectly on the interstitium to stimulate localized differentiation of endogenous spermatogonia.

The radiation-induced block in spermatogonial differentiation is due to damage to the somatic environment, not the germ cells

Radiation and chemotherapeutic drugs cause permanent sterility in male rats, not by killing most of the spermatogonial stem cells, but by blocking their differentiation in a testosterone-dependent manner. However, it is not known whether radiation induces this block by altering the germ or the somatic cells. To address this question, we transplanted populations of rat testicular cells containing stem spermatogonia and expressing the green fluorescent protein (GFP) transgene into various hosts. Transplantation of the stem spermatogonia from irradiated adult rats into the testes of irradiated nude mice, which do not show the differentiation block of their own spermatogonia, permitted differentiation of the rat spermatogonia into spermatozoa. Conversely transplantation of spermatogonial stem cells from untreated prepubertal rats into irradiated rat testes showed that the donor spermatogonia were able to colonize along the basement membrane of the seminiferous tubules but could not differentiate. Finally, suppression of testosterone in the recipient irradiated rats allowed the differentiation of the transplanted spermatogonia. These results conclusively show that the defect caused by radiation in the rat testes that results in the block of spermatogonial differentiation is due to injury to the somatic compartment. We also observed colonization of tubules by transplanted Sertoli cells from immature rats. The present results suggest that transplantation of spermatogonia, harvested from prepubertal testes to adult testes that have been exposed to cytotoxic therapy might be limited by the somatic damage and may require hormonal treatments or transplantation of somatic elements to restore the ability of the tissue to support spermatogenesis.

Radiation exposure impairs luteinizing hormone signal transduction and steroidogenesis in cultured human leydig cells

Therapeutic, accidental, and experimental radiation exposures decreased serum testosterone in males, leading to various sexual problems. Since testicular Leydig cells are the predominant source of circulating testosterone, findings on the direct effects of radiation on Leydig cell steroidogenesis and the mechanism behind such effects would be of greater importance to the use of safer radiation doses in cancer therapy and to adopt preventive or therapeutic measures to alleviate postirradiation lesions, respectively. Therefore, this study was undertaken to explore the same using cultured human Leydig cells. Testicles removed from advanced prostatic carcinoma patients were used for isolation and purification of Leydig cells. Purified Leydig cells were cultured and then exposed to different doses (2, 4, 6, 8, and 10 Gy) of fractioned gamma radiation. Normal and irradiated cells were used for luteinizing hormone (LH) receptor quantification or total RNA isolation to study LH receptor mRNA expression or LH/cyclic AMP (cAMP) stimulation test. While LH-stimulated cells were used for cAMP assay, LH- and cAMP-stimulated cells were used for the estimation of steroidogenic enzymes, testosterone and estradiol production. Radiation exposure caused adverse effects on Leydig cell steroidogenesis in a dose-dependent manner. While lower doses (2 and 4 Gy) were ineffective, higher doses (6 Gy and above) drastically decreased LH receptor, basal and LH-stimulated cAMP generation, and basal, LH-, and cAMP-stimulated steroidogenesis. While 2 Gy of radiation exposure increased the LH receptor mRNA level, other doses did not induce any significant change. Therefore, it is concluded that higher doses of radiation impair Leydig cell steroidogenesis by affecting LH signal transduction at the level of both pre- and post-cAMP generation. Decreased level of LH receptors following higher doses of radiation exposure is not coupled with impaired expression of its mRNA.

Testicular edema is associated with spermatogonial arrest in irradiated rats

Irradiation of LBNF1 rat testes induces arrest of spermatogonial differentiation, which can be reversed by suppression of testosterone with GnRH antagonist treatment. The cause of the arrest is unknown. We investigated the time course and hormonal effects on radiation-induced arrest and changes in interstitial fluid volume. We postulated that the edema evident in irradiated testes caused the differentiation blockade. Rat testes were irradiated with 3.5 or 6 Gy. Interstitial fluid testosterone (IFT) increased between 2 and 6 wk after irradiation, followed by increased interstitial fluid volume at 6 wk and spermatogonial blockade at 8 wk. Additional rats irradiated with 6 Gy were given GnRH antagonist, alone or with exogenous testosterone, for 8 wk starting at 15 wk after irradiation. In rats treated with GnRH antagonist, IFT started falling within 1 wk of treatment, followed by interstitial fluid volume decreases at wk 2 and 3, with recovery of spermatogenesis starting at wk 4. Addition of exogenous testosterone largely blocked the effects of GnRH antagonist on IFT, interstitial fluid volume, and spermatogenesis. Thus the testicular edema was largely modulated by intratesticular testosterone levels. The time course of changes in the spermatogonial blockade more closely followed that of the testicular edema than of IFT, indicating that testosterone may block spermatogonial differentiation indirectly by producing edema. This conclusion was further supported by an experiment in which irradiated rats were treated with GnRH antagonist plus estrogen; the treatment further reduced IFT and interstitial fluid volume and reduced the time to initiation of recovery of spermatogonial differentiation. These results suggest that studies of the edematous process or composition of the fluid would help elucidate the mechanism of spermatogonial arrest in toxicant-treated rats.

Effects of gamma radiation on luteinizing hormone (LH) receptor expression, signal transduction and steroidogenesis in cultured rat Leydig cells

PURPOSE

To investigate the dose-dependent effects of gamma radiation on rat Leydig cell luteinizing hormone (LH) receptor expression, signal transduction and steroidogenesis.

MATERIALS AND METHODS

Leydig cells isolated from testicles of adult male albino rats were cultured and exposed to different doses (2, 4, 6, 8 and 10 Gy) of fractioned gamma radiation for three days. Normal as well as irradiated cells were used for the quantification of cell surface LH receptor or LH/cyclic adenosine monophosphate (cAMP) stimulation test or total ribonucleic acid (RNA) isolation to study the LH receptor messenger RNA (mRNA) expression by reverse transcriptase polymerase chain reaction (RT-PCR).

RESULTS

Radiation was found to have dose-dependent effects on rat Leydig cell surface LH receptor, basal and LH-stimulated cAMP production, basal, LH and cAMP-stimulated steroidogenesis. Lower doses (2 and 4 Gy) of radiation did not induce any change, whereas higher doses (6, 8 and 10 Gy) of radiation exposure diminished the above said parameters significantly. In spite of the low level of cell surface LH receptors following higher doses of radiation exposure, its mRNA level was not altered under any dose level.

CONCLUSION

From these observations, it is concluded that gamma radiation has dose-dependent inhibitory effects on Leydig cell LH signal transduction and steroidogenesis. Decreased cell surface LH receptor following higher doses of radiation exposure is not coupled with altered LH receptor mRNA level.

Rat testis as a radiobiological in vivo model for radionuclides

The radiobiological effect of intracellularly localised radionuclides emitting low energy electrons (Auger electrons) has received much attention. Most in vivo studies reported have been performed in the mouse testis. We have investigated the rat testis as an in vivo radiobiological model, with sperm-head survival, testis weight loss and also alteration in the blood plasma hormone levels of FSH and LH as radiobiological endpoints. Validation of the rat testis model was evaluated by using mean absorbed doses of up to 10 Gy from intratesticularly (i.t.) injected (111)In oxine or local X-ray irradiation. Biokinetics of the i.t. injected radionuclide was analysed by scintillation camera imaging and used in the absorbed dose estimation. By the analysis of the autoradiographs, the activity distribution was revealed. Cell fractionation showed (111)In to be mainly associated with the cell nuclei. External irradiations were monitored by thermoluminescence dosimeters. The sperm-head survival was the most sensitive radiobiological parameter correlated to the mean absorbed dose, with a D(37) of 2.3 Gy for (111)In oxine and 1.3 Gy for X rays. The levels of plasma pituitary gonadal hormones FSH and LH were elevated for absorbed doses >7.7 Gy. This investigation shows that the radiobiological model based on the rat testis has several advantages compared with the previously commonly used mouse testis model. The model is appropriate for further investigations of basic phenomena such as radiation geometry, intracellular kinetics and heterogeneity, crucial for an understanding of the biological effect of low-energy electrons.

Both testosterone and follicle-stimulating hormone independently inhibit spermatogonial differentiation in irradiated rats

Simultaneous suppression of both testosterone and FSH with GnRH antagonists (GnRH-ant) reverses the radiation-induced block in spermatogonial differentiation in F1 hybrids of Lewis and Brown-Norway rats. Although addition of exogenous testosterone restores the block, it also raises FSH, and hence it had not been possible to conclusively determine which hormone was inhibiting spermatogonial differentiation. In the present study, we establish the relative roles of testosterone and FSH in this inhibition using three different approaches. The first approach involved the treatment of irradiated rats, in which differentiation was stimulated by GnRH-ant plus flutamide, with FSH for 2 wk; the FSH reduced the percentage of tubules that were differentiated (TDI) by about 2-fold, indicating that FSH does have an inhibitory role. The second approach involved treatment of irradiated, hypophysectomized rats with exogenous testosterone for 10 wk; testosterone also reduced the TDI, demonstrating that testosterone had a definite inhibitory effect, independent of pituitary hormones. Furthermore, in this protocol we showed that TDI in the hypophysectomized testosterone-treated group, which had higher intratesticular testosterone levels but lacked FSH, was slightly higher than the TDI in a GnRH-antagonist-testosterone-treated group of irradiated rats, which had normal physiological levels of FSH; this result supports a role for endogenous FSH in suppressing spermatogonial differentiation in the latter group. The third approach involved injection of an active anti-FSH antibody for 10 d in untreated, GnRH-ant plus flutamide-treated, or GnRH-ant plus testosterone-treated irradiated rats. This was not sufficient to increase the TDI. However, flutamide given in a similar treatment schedule did increase the TDI in GnRH-ant plus testosterone-treated rats. We conclude that both testosterone and FSH individually inhibit spermatogonial differentiation after irradiation, but testosterone is a more highly potent inhibitor than is FSH.

Effects of medroxyprogesterone and estradiol on the recovery of spermatogenesis in irradiated rats

Suppression of intratesticular testosterone (ITT) levels is required for spermatogenic recovery in rats after irradiation, but maintenance of peripheral testosterone (T) levels is important for many male functions. Considering the preservation of peripheral T while suppressing ITT, we tested the effects of a combination of a progestin, medroxyprogesterone acetate (MPA), plus T on spermatogenic recovery after irradiation, and compared its effects to those of T alone or T combined with estradiol (E2). Rats were given testicular irradiation (6 Gy) and treated during wk 3-7 after irradiation with MPA + T, or the individual steroids with or without GnRH antagonist (GnRH-ant), or GnRH-ant alone, or T + E2. Whereas GnRH-ant alone stimulated differentiation in 55% of tubules 13 wk after irradiation compared with 0% in irradiated-only rats, the addition of MPA reduced the percentage of tubules showing differentiation to 18%. However, T or MPA alone or the combination of the two induced germ cell differentiation in only 2-4% of tubules. In contrast, E2 stimulated differentiation in 88% of tubules, and T combined with E2 still resulted in differentiation in 30% of tubules. Although both MPA and E2 suppressed ITT levels to approximately 2% of control (2 ng/g testis), MPA was a less effective stimulator of spermatogenic recovery than E2 or GnRH-ant alone. MPA's function as a weak androgen was likely responsible for inhibiting spermatogenic recovery, as was the case for all other tested androgens. Thus, for clinical protection or restoration of spermatogenesis after radiation or chemotherapy by suppressing T production, MPA, at least in the doses used in the present study, is suboptimal. The combination of an estrogen with T appears to be most effective for stimulating such recovery.

Increased levels of comet-detected spermatozoa DNA damage following in vivo isotopic- or X-irradiation of spermatogonia

To investigate whether DNA damage arising in spermatogenic germ cells can be detected in resultant sperm, we have irradiated murine testis and collected spermatozoa from the vas deferens 45 days later. These cells were derived from spermatogonia present at the time of irradiation. Two forms of irradiation were used, external X-rays (4Gy) and internal auger electrons from contamination of the male mouse with the isotope Indium-114m (1.85MBq), which was localised in the testis. Both forms of irradiation produced a profound fall in vas deferens sperm count and testis weight, Indium-114m being more effective. Using the neutral Comet assay for double strand break detection, significant increases in sperm comet tail length and moment were observed. The levels of damage were similar for both treatments. Care had to be taken during the assay to distinguish between sperm and somatic cells as the proportion of the latter increased after irradiation. We conclude that the comet assay can detect DNA damage in spermatozoa after the in vivo exposure of male germ cells to a known testicular genotoxic agent. The assay may be useful for the assessment of sperm DNA damage (double stranded) associated with male infertility and post-fertilization developmental abnormalities in the offspring.

Gonadal function of young adults after therapy of malignancies during childhood or adolescence

As the survival rate of children with malignancies has increased over past decades, the follow up of adult long-term survivors (LTS) of childhood cancer should focus on late effects of disease and treatment. Gonadal function was therefore studied in 54 LTS (aged 17-29 years; 33 male, 21 female) 2-18 years after treatment for malignancies during childhood or adolescence. To analyse the sensitivity of different diagnostic methods, tests of endocrine function (n = 52), spermiograms (n = 14), gynaecological status (n = 20) and ultrasonography of the gonads (n = 53) were compared with the results of equivalent tests in 23 age-matched normal controls (12 male, 11 female). There were no differences between male and female LTS concerning age at diagnosis, gonadal dose of irradiation (XRT) and doses of applied chemotherapeutic agents. Whereas male LTS had elevated levels of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) before (P < 0.05; P < 0.001) and after (P < 0.01; P < 0.001) stimulation with gonadotropin releasing hormone, female LTS exhibited normal endocrine function. Accordingly, male patients exhibited lower testicular volumes than normal controls, as measured with a Prader orchidometer (P < 0.01) or by ultrasonography (P < 0.001). Gynaecological status and ultrasonography of the gonads were normal in female LTS and controls. Whereas all spermiograms of normal controls (n = 8) showed a normal sperm cell density (SCD), only 2 of 14 male LTS exhibited a normal SCD (P < 0.001). Azoospermic LTS (n = 9) had been treated more often with alkylating agents and had received higher (P < 0.05) gonadal doses of XRT. All male LTS with testicular volumes below the normal range (< 13 ml) and basal FSH levels above the normal range (> 10 IU/l) exhibited azoospermia, whereas LTS with normal values for testicular volume and basal FSH had a normal SCD.

CONCLUSION

A sex-specific susceptibility for gonadal damage after treatment for malignancies might be responsible, in part, for the impaired gonadal function of male LTS. Therapy with alkylating agents and/or high gonadal doses of XRT were important risk factors for azoospermia. A simple method to estimate potential fertility in individual LTS is to measure testicular volume, using a Prader orchidometer, and basal FSH serum levels.

Testicular toxicity of the transferrin binding radionuclide 114mIn in adult and neonatal rats

Adult (70 d) and neonatal (7 d) male rats were dosed (i.p.) with 37 MBq/kg (1 mCi/kg; approximately 1 microgram elemental indium/kg) 114mIn, a transferrin-binding radionuclide. In adults, approximately 0.25% of the injected activity localised within the testis by 48 h postinjection and remained constant for up to 63 d. In neonates, 0.06% of the activity was in the testis by 48 h, and this declined such that by 63 d only 0.03% remained. At 63 d, treated rats had reduced sperm head counts and abnormal testicular histology that was more marked in animals dosed as adults than as neonates. In vitro, uptake of 114mIn into seminiferous tubules isolated from 7-, 20-, or 70-d-old rats was compared with that of 125I. Both radionuclides were readily accumulated by the tubules. Whilst 114In uptake into 20- and 70-d tubules was inhibited by excess transferrin, uptake into 7-d tubules was unchanged. 125I uptake was not affected by excess transferrin. These data support the contention that some radionuclides may cross the blood-testis barrier by utilisation of the physiologic iron-transferrin pathway, which may lead to greater testicular damage in adult compared to neonatal animals.

Stage-specific cellular regulation of inhibin alpha-subunit mRNA expression in the rat seminiferous epithelium

To find out the local regulation of inhibin production and its possible paracrine role in the seminiferous epithelium, inhibin alpha mRNA levels were measured in sequential 1 mm segments of rat seminiferous tubules accurately staged by transillumination technique. Highest levels were found at stages XIV-I-IV of the cycle, and lowest at stages VI-VIIb of the cycle. When dividing spermatogonia were selectively destroyed by 3 Gy of high-energy X-irradiation, stage-specific inhibin alpha mRNA levels remained unchanged until 26 and 38 days after irradiation when stages VII and VIII of the cycle showed 6- and 4-fold increases during a selective reduction of pachytene spermatocyte and round spermatid numbers, respectively. The results suggest that these cells at a strictly stage-specific fashion have a paracrine inhibitory effect on Sertoli cell inhibin alpha gene expression. Inhibin alpha mRNA level also correlates closely to the follicle-stimulating hormone-stimulated cAMP production during the cycle of the seminiferous epithelium, but does not seem to have a correlation to spermatogonial DNA synthesis.

Golden hamster myoid cells during active and inactive states of spermatogenesis: correlation of testosterone levels with structure

Myoid cells were examined quantitatively in adult golden hamsters with active spermatogenesis and compared with hamsters in which the testes were regressed due to a modification in the light-dark cycle. A detailed morphometric study was undertaken utilizing animals previously examined. The cell-surface area and volumes of most organelles were not significantly different in animals which were gonadally active as compared with regressed animals. A slight, but significant, increase in nuclear volume (31%) and a slight, but significant, decrease (28%) in cell volume were recorded for regressed animals. The total volume of pinocytotic vesicles was increased dramatically (approximately threefold) in active animals in comparison with inactive animals (P less than 0.01), indicating that an increase in non-specific transport across the myoid cell is associated with spermatogenic activity. Intravascularly injected horseradish peroxidase was capable of entering pinocytotic vesicles in both active and inactive animals. Plasma luteinizing hormone (LH) as well as plasma and testicular testosterone levels were weakly (r = 0.64, 0.68, and 0.65, respectively), but significantly (P less than 0.05), correlated with cell size. Plasma and testicular testosterone were correlated with the total volume of pinocytotic vesicles (r = 0.74 and 0.68, respectively). The data indicate that although the rat myoid cell possesses receptors for testosterone, there are few structural manifestations of the hamster myoid cell that correlate well with testosterone levels. Thus, the hamster myoid cell differs from two other hormone-responsive somatic cells in the testis, the Sertoli cell and the Leydig cell, that show dramatic structural alterations with changes in gonadal activity and striking correlations of structural features with functional measures.(ABSTRACT TRUNCATED AT 250 WORDS)

Prolonged suppression of spermatogenesis by oestrogen does not preserve the seminiferous epithelium in procarbazine-treated rats

We examined the hypothesis that induction of reversible testicular atrophy, subsequent to withdrawal of gonadotrophin support, would alleviate the testicular toxicity of the anti-cancer drug procarbazine. In rats, severe but reversible testicular atrophy and suppression of spermatogenesis were induced 56 days after the subcutaneous insertion of a silastic implant containing oestradiol-17 beta. The effect of this treatment upon the testicular toxicity of four weekly doses of procarbazine (200 mg kg-1) was examined 56 days after the termination of procarbazine/oestrogen treatment. At this time the testicular endocrine and spermatogenic functions were close to normal in rats which has received only oestradiol-17 beta. Procarbazine produced severe testicular atrophy which was associated with azoospermia and destruction of the germinal epithelium. Serum LH and FSH concentrations were raised and were associated with low serum concentrations of both testosterone and androgen-binding protein. The combination of procarbazine with the oestrogen treatment did not change any of the testicular toxicity and in some cases it appeared to be exacerbated. In contrast to these experiments other studies have indicated that the testis can be protected if spermatogenesis is reversibly suppressed by other agents which are also active via the pituitary endocrine system. The data would therefore suggest that protection is achieved either by some testicular change other than withdrawal of pituitary gonadotrophin support or that oestradiol-17 beta has additional activity which is permissive for the development of the testicular toxicity of procarbazine.

A comparative study in twelve mammalian species of volume densities, volumes, and numerical densities of selected testis components, emphasizing those related to the Sertoli cell

Morphometric studies were performed on 12 mammalian species (degu, dog, guinea pig, hamster, human, monkey, mouse, opossum, rabbit, rat, stallion, and woodchuck) to determine volume density percentage (Vv%), volume (V), and numerical density (Nv) of seminiferous tubule components, especially those related to the Sertoli cell, and to make species comparisons. For most species, measurements were taken both from stages where elongate spermatids were deeply embedded within the Sertoli cell and from stages near sperm release where elongate spermatids were in shallow crypts within the Sertoli cell. Montages, prepared from electron micrographs, were used to determine Vv% of Sertoli cell components in seminiferous tubules. Excluding the tubular lumen, the Sertoli cell occupied from a high of 43.1% (woodchuck) to a low of 14.0% (mouse) of the tubular epithelium. There was a strong negative correlation (r = -0.83; P less than 0.005) of volume occupancy of Sertoli cells with sperm production. Nuclear volume, as determined by serial reconstruction using serial thick sections, ranged from a high of 848.4 microns 3 (opossum) to a low of 273.8 microns 3 (degu). There was no correlation (r = 0.02) of nuclear volume with volume occupancy (Vv%) in the tubule. Sertoli cell volume was determined by point-counting morphometry at the electron-microscope level as the product of the nuclear size and points determined over the entire cell divided by points over the nucleus. Sertoli cell V ranged from 2,035.3 microns 3 (degu) to 7,011.6 microns 3 (opossum) and was highly correlated (r = 0.85; P less than 0.001) with nuclear size. However, there was no significant correlation between the Sertoli cell size (V) and volume occupancy (Vv%; r = 0.13) or sperm production (r = -0.21). Stereological estimates of the numerical density (Nv) of Sertoli cells ranged from a high of 101.9 x 10(6) (monkey) to a low of 24.9 x 10(6) (rabbit) cells per cm3 of testicular tissue. There was no correlation of numerical density of Sertoli cells with sperm production (r = 0.002). A negative correlation was, however, observed between the numerical density of the Sertoli cells and the Sertoli cell size (r = -0.79; P less than 0.002). Data from the present study are compared with those previously published. This is the first study to compare Sertoli cell morphological measurements using unbiased sampling techniques. Morphometric data are provided which will serve as a basis for other morphometric studies.

The reproductive system of male rats exposed to very low doses of ionizing radiation, 1: Hormonal profile of animals exposed after sexual maturity

Adult male rats were treated with a single, whole body exposure to a dose of 0.001, 0.01 or 0.1 Gy (1 Gy = 100 rad). The animals were sacrificed 1, 7, 30, 100 or 180 days following exposure. Serum testosterone, serum and hypophyseal LH, FSH and prolactin as well as hypothalamic LHRH were measured. In the 0.1 Gy irradiated rats, serum LH and FSH were 100% higher and serum prolactin was 30% lower as compared to controls, 30 days after irradiation. The concentrations of these hormones remained significantly different from control values even after 180 days after exposure. On the other hand, the hypophyseal content of LH, FSH and prolactin decreased in the 0.1 Gy treated rats, 100 days after irradiation. In the group of the 0.01 Gy irradiated rats, serum FSH increased by 70% and hypophyseal FSH decreased. No changes were observed in serum testosterone and hypothalamic LHRH in any of the irradiated groups and no changes were observed in the group exposed to 0.001 Gy. It may be concluded that a long term damage to the reproductive system of the male rat was induced by a single, whole body exposure to 0.1 Gy of gamma radiation.

Steroidogenesis in the testes and the adrenals of adult male rats after gamma-irradiation in utero at late pregnancy

Pregnant rats were irradiated with 2.1 Gy gamma-ray of 60Co at day 20 of gestation. Seventy days after birth, the body weight of the fetally irradiated male pups was significantly lower than the control. The testes, ventral prostates and seminal vesicles were atrophied by irradiation, whereas no decreased weight of the adrenals was observed. Histological examination of the testes of the irradiated rats revealed a complete disappearance of germinal cells. Sertoli cells and Leydig cells appeared normal, and no apparent histological difference was observed in the adrenals between the control and the irradiated rats. Activities of microsomal delta 5-3 beta-hydroxysteroid dehydrogenase (HSD) + isomerase, 17 alpha-hydroxylase/C17,20-lyase, 17 beta-HSD and 7 alpha-hydroxylase per pair of testes were decreased in the irradiated rats (36-86% of the control). In contrast, no decreased activity of 20 alpha-HSD in the cytosol fraction was observed by irradiation. No decreased activity of adrenocortical enzymes, such as delta 5-3 beta-HSD + isomerase, 21-hydroxylase, 11 beta-/18-hydroxylase and 5 alpha-reductase, was also observed in the irradiated group. Concentrations of LH, FSH, TSH, prolactin, testosterone, progesterone and aldosterone in serum were measured by radioimmunoassay. Only the FSH concentration was significantly increased by the irradiation, while no difference was found in the concentration of other hormones. It was concluded that irreversible damage was induced in spermatogenesis and androgen production by the fetal irradiation, whereas corticoidogenesis was not affected.

Changes in the testicular microvasculature during photoperiod-related seasonal transition from reproductive quiescence to reproductive activity in the adult golden hamster

The structure and permeability of the testicular microvasculature in the adult golden hamster during different phases of gonadal activity was examined. After 12 weeks of exposure to a short photoperiod (SD; 6L:18D), maximal testicular regression with over tenfold reduction in size was achieved as compared with active testes of animals maintained in long photoperiod (LD; 16L:8D). Testes weights and volumes in regressed testes were not significantly different from the values measured in animals undergoing early recrudescence (transfer from SD to LD for 1 or 2 weeks). The volume density of testicular blood vessels and their lumina did not differ significantly between fully gonadally active, fully regressed animals or those transferred from SD to LD for 2 weeks. However, in animals transferred for 1 week from SD to the stimulatory LD, the density of testicular blood vessels and vascular permeability to the endothelial tracer horseradish peroxidase were significantly increased, as compared to all other groups. An angiogenic process was observed by electron microscopy, which was initiated in the regressed gonad and which was prominent 1 week after transfer from SD to LD, but it was less conspicuous 2 weeks after transfer from SD to LD. The angiogenic process was characterized by activated developing blood vessels with a basal lamina and a lumen, which was formed by dilatation of an interendothelial space. There were two types of endothelial sprouts: the first with one layer of basal lamina, indicating true neovascularization, and the second with additional layers of basal lamina. In the latter, the presence of a superfluous basal lamina indicates that regeneration takes place along the path of old vessels. In fully regressed animals isolated basal-lamina-like structures were observed. Basal laminae are known to survive endothelial cell death, and these basal laminae later appear to serve as a scaffold for regeneration of new vessels. The rapid renewal of the testicular microvasculature under physiological stimuli suggests that the recrudescing testis of the golden hamster can be viewed as a physiological model of angiogenesis.

Strain-dependency of procarbazine-induced testicular toxicity

Three strains of rat were used to examine strain-dependency of procarbazine-induced testicular toxicity. CCFHB and CCFY1 outbred albino rats and inbred PVG piebald variegated rats were treated weekly with procarbazine (200 mg/kg/dose x 4). Fifty-six days later, the rats were killed and reproductive parameters evaluated. Strain-related differences in body, testis, prostate, seminal vesicle weights, testis sperm, intratesticular testosterone, and [125I]hCG binding to testicular LH receptors were observed. Although treatment with procarbazine affected testis function in all strains, significant interactions occurred between treatment and strain. LH receptor binding and stem-cell survival were more severely affected in the inbred strain than in outbred strains. Serum testosterone increased in the outbred strain but decreased in the inbred strain, generating an interaction that obscured possible main effects. Significant strain-related differences in within-group variances demonstrated that measurements were more variable in the outbred strains than in the inbred strain. Testes of the inbred strain appeared to be more sensitive to the effects of procarbazine than those of the outbred strains. These data illustrate two important toxicologic phenomena: differences in response variability and differences in target-organ sensitivity, both of which were explained by genetic variability.

Response of the seminiferous epithelium to scattered radiation in seminoma patients

Semen and blood samples were obtained, at 3-month intervals over 12 to 28 months, from patients who underwent subdiaphragmal radiation after orchidectomy for seminoma testis. Before radiotherapy a mean (+/- SE) semen volume of 4.7 +/- 0.5 ml, a mean sperm count of 44.4 +/- 13.5 x 10(6)/ml, a mean percentage of motile cells of 20.3 +/- 5.2, a mean percentage of morphologically normal spermatozoa of 13.4 +/- 5.4, a mean percentage of swollen sperm of 39.6 +/- 7.4, and a mean serum follicle-stimulating hormone (FSH) value of 8.3 +/- 1.2 mIU/ml was found. The mean testicular dose from scatter was 62 +/- 5 cGy (range, 34 to 95 cGy). Sperm counts between 0 and 2.75 x 10(6)/ml were seen at 6.8 +/- 0.6 months and recovery to values greater than 2.25 x 10(6)/ml at 11.8 +/- 0.8 months after the start of radiation. Peak FSH values of 19.2 +/- 1.6 mIU/ml were obtained at 6.7 +/- 0.9 months after the start of irradiation. After recovery mean semen volume was 3.9 +/- 0.4 ml, mean sperm count 34.6 +/- 5.6 x 10(6)/ml, the mean percentage of motile cells 42.5 +/- 6.0, the mean percentage of swollen sperm 58.7 +/- 6.8, and the mean percentage of spermatozoa with normal morphology 23.4 +/- 5.1. Only motility was significantly different (P less than 0.01) from pretreatment values. The elevation of FSH values with time after start of radiotherapy reflected the toxicity to spermatogenesis but no correlation was found between peak FSH levels and scattered radiation dose. Also, neither the time from start of radiotherapy to sperm count nadir or recovery nor the time to peak FSH levels was significantly correlated with radiation dose.

Spermiogenesis in the red-ear turtle (Pseudemys scripta) and the domestic fowl (Gallus domesticus): a study of cytoplasmic events including cell volume changes and cytoplasmic elimination

Nuclear and cytoplasmic volume changes as well as the elimination of residual spermatid cytoplasm were investigated in the red-ear turtle (Pseudemys scripta) and the rooster (Gallus domesticus). Nuclei of newly formed spermatids which were originally centrally located became eccentrically located within the cell in both species. Shortly thereafter the nuclear pole of the spermatid was found situated within deep crypts of a Sertoli cell. The cytoplasm of elongating spermatids was displaced along the nonacrosomal region of the nucleus and the proximal flagellum. In both species sheetlike Sertoli cell processes indented spermatid cytoplasm adjacent to the nucleus and appeared to segregate small packets of the cytoplasm. In the turtle, these packets of cytoplasm were separated from the spermatid. In both the turtle and rooster, a portion of the spermatid cytoplasm was displaced forward over the acrosomal region of the spermatid to resemble a hood. As spermatids were transported to the seminiferous tubular lumen, cytoplasmic lobes which projected forward of the spermatid head were formed by preferential flow of cytoplasm into one aspect of the cytoplasmic hood. In both species, at sperm release the cytoplasmic lobe was disengaged from the spermatid head to form a large residual body that was internalized and degraded within the Sertoli cell. Medium-sized cytoplasmic lobes were pinched from the head and neck region of the turtle and rooster spermatids, respectively. In the turtle, small-sized mitochondrial-rich cytoplasmic fragments budded from the caudal head and midpiece of the spermatids and were phagocytosed by the Sertoli cell. Thus, cytoplasmic elimination occurred through 1) segregation of cytoplasmic packets by Sertoli penetrating processes (turtle), 2) elimination of large and medium-sized residual bodies from the head (turtle and bird), and 3) budding of small mitochondrial-rich cytoplasmic fragments from the region of the midpiece (turtle). In the turtle a 79% reduction in total cell volume occurred during spermiogenesis which was the result of an 84% cytoplasmic reduction and a 78% nuclear reduction. During spermiogenesis, the rooster lost 97% of its total cell volume due to a 97% cytoplasmic volume change and a 96% nuclear volume change.

Changes in testicular and serum hormone concentrations in the male rat following treatment with m-dinitrobenzene

m-Dinitrobenzene (m-DNB)-induced testicular atrophy has been attributed to a direct effect upon the germinal epithelium. However, such degenerative changes in the germinal epithelium should induce shifts in the testicular hormonal milieu, which would in turn alter the hypothalamic-pituitary gonadal axis in general. This study evaluated the endocrine status of male rats (killed 3 hr, 24 hr, 1 week, and 2 weeks) following a single oral dose of m-DNB (32 mg m-DNB/kg). Serum and pituitary leuteinizing hormone, follicle-stimulating hormone (FSH), and protactin and hypothalamic gonadotropin-releasing hormone (GnRH) concentrations were determined. Testosterone and androgen-binding protein concentrations in serum, interstitial fluid, seminiferous tubule fluid, and caput epididymis were also determined. In vitro basal and hCG-stimulated testosterone release was determined in the decapsulated testis. Results of the present study indicate that pituitary hormone concentrations and hypothalamic GnRH were unaffected after a single oral dose of m-DNB. Serum FSH was elevated at 2 weeks. There was a transient decrease in serum testosterone at 24 hr, which returned to control values at 1 and 2 weeks. Interstitial fluid, seminiferous tubule fluid, and caput epididymal testosterone concentrations were increased at 1 and 2 weeks. Basal testosterone release in vitro was increased at 2 weeks, while hCG-stimulated testosterone release was increased at 1 and 2 weeks. Androgen-binding protein concentrations in serum and interstitial fluid were increased at 1 and 2 weeks. Androgen-binding protein was increased at 24 hr and 1 week in seminiferous tubule fluid, but returned to control concentrations by 2 weeks. However, the total tubular content of androgen-binding protein was dramatically decreased at 2 weeks. Androgen-binding protein in the caput epididymis was unaltered following m-DNB treatment. These data demonstrate that m-DNB exerts a direct effect on the testes and not through alterations in hypothalamic and pituitary control of gonadal function.

Protection from radiation-induced damage to spermatogenesis in the androgen pretreated rat

Protection of spermatogenesis from radiation-induced damage has been investigated in the adult Wistar rat. Silastic tubing containing either cholesterol or testosterone was implanted subcutaneously 7 weeks before 4 equal daily fractions of either 1, 1.5, 2, and 2.5 Gy of 230 kVp X-rays locally to the testes. Implants were removed on the day following the last fraction and 8 weeks after irradiation 88.6%, 83.8%, 63.6% and 28.9% tubule cross-sections respectively were found regenerating in rats pretreated with testosterone. In contrast, 68.45%, 58.6%, 38.2% and 17.3% tubule cross-sections regenerating were obtained in rats pretreated with cholesterol. Changes in testis weight however were found to show the reverse trend (i.e. a greater weight loss was observed following androgen pretreatment). These results show that protection of spermatogenesis from fractionated irradiation may be achieved in rat testis by androgen pretreatment.

Effects of cytochalasin D on the integrity of the Sertoli cell (blood-testis) barrier

Ectoplasmic specializations (ES) containing packed actin microfilaments are associated with the numerous parallel rows of occluding junctions which form the Sertoli cell (blood-testis) barrier. To determine if ES regulate the structure of the occluding junctions and/or barrier permeability, we experimentally disrupted ES microfilaments in vivo with intratesticularly injected cytochalasin D (CD). Electron microscopic observations of seminiferous tubules from CD-treated (150-500 microM CD; 0.5-12 hr) animals indicated that ES was absent from regions where the Sertoli cell barrier is located. Seminiferous epithelial sheets from uninjected or vehicle-injected animals (1 DMSO: 1 saline) stained with NBD-phallacidin demonstrated the presence of patterned ES actin surrounding the basolateral regions of adjacent Sertoli cells. After exposure to CD, epithelial sheets exhibited increasingly patchy fluorescence indicating progressive F-actin disruption. Freeze-fracture replicas of CD-injected testes revealed numerous focal alterations in the region of occluding junctions which included disorganization of the parallel arrangement of junctional rows, the presence of free-ending rows, clustering of intramembranous particles (IMPs) between rows, reduction in the number of rows, and loss of IMPs on both the P-face and E-face. Tracer experiments, following CD exposure, were conducted to test the integrity of occluding junctions: lanthanum hydroxide, dextrose, or filipin was added, in separate experiments, to the fixative during perfusion-fixation. In another study, serum containing an antibody against adluminal germ cells was injected intratesticularly, and frozen sections were processed for immunofluorescence study. A final study consisted of simultaneous intratesticular infusions of CD and radiolabelled inulin with subsequent intraluminal and peritubular fluid sampling. In animals which were injected with CD, lanthanum was found to enter the adluminal compartment; fixative made hypertonic by addition of dextrose caused germ cells within the adluminal compartment to shrink and produce exaggerated intercellular spaces; filipin-cholesterol perturbations were present between some Sertoli cell junctional rows and on spermatid plasma membranes; and IgG was detected within the adluminal compartment of many seminiferous tubules. None of these adluminal manifestations was noted in control animals or those which received vehicle. Quantitatively, in the in vivo micropuncture experiments, significantly more radiolabelled inulin entered the lumen of seminiferous tubules from CD-treated animals than from those exposed to vehicle.(ABSTRACT TRUNCATED AT 400 WORDS)

Lack of protection by oestrogen from radiation-induced testicular damage in the rat

The influence of pretreatment with oestradiol dipropionate (E) on the response of the rat testis to radiation has been studied. Treatment of rats for 3 weeks with E (100 mg/kg per week) induced severe atrophy of the testis. At this time, the testes were locally irradiated to doses of 0, 4 or 15 Gy, E treatment was continued for a further week and the rats were killed 24 or 36 weeks later. Radiation alone had a marked effect on spermatogenesis as assessed by testicular weight and counts of regenerating tubule cross-sections. At 24 weeks, 8% of cross-sections were found to possess spermatogenic cells after 4 Gy and this had increased to 15% at 36 weeks. No significant regeneration was observed after 15 Gy. Similar results were obtained in those rats pretreated with E. Following irradiation alone, decreases in interstitial cell numbers and testicular luteinizing hormone (LH) receptors reflected Leydig cell damage. Again, pretreatment with oestrogen did not appear to reduce Leydig cell damage. The results of the present study suggest that pretreatment with oestrogen is not able to reduce the testicular damage induced by moderate to high single doses of radiation.

Delayed effects of doxorubicin on spermatogenesis and endocrine function in rats

Doxorubicin was administered to adult male Wistar rats (1 mg/kg body weight, three times per week, for one, two, three, or four weeks) in order to examine testicular and reproductive endocrine toxicity 56 days after treatment. Doxorubicin treatment produced persistent dose-related reductions in testis, epididymis, and seminal vesicle weights, but did not alter ventral prostate weight. Testis and serum testosterone levels were not significantly affected by treatment, but serum LH was increased after treatment, and binding of iodinated hCG to testicular LH receptors was reduced. Serum FSH was elevated by the two lower total administered doses, but was not different from controls after treatment with the two higher total doses. There was clear histologic evidence of dose-dependent damage to the seminiferous tubules, which was reflected by decreased testicular and epididymal sperm content and by reductions in the stem-cell survival index. These results indicate that doxorubicin produces significant and persistent damage to the endocrine and spermatogenic compartments of the testis.

Effect of sexual maturity on testicular injury subsequent to procarbazine administration in rats

The present study examined the effect of age on various aspects of Leydig cell and Sertoli cell function in Sprague-Dawley rats administered procarbazine. Procarbazine was administered intraperitoneally to Sprague-Dawley rats aged 14, 24, and 60 days in 3 weekly injections of 200 mg/kg. Animals were sacrificed 1 week after the last injection. Severe impairment of spermatogenesis was evident in all animals. Sertoli cell function, as assessed by total testicular ABP content, was not significantly different between procarbazine-treated animals and controls in any age group. On the other hand, procarbazine administration resulted in a 60% reduction in total intratesticular testosterone content in the 14-day-old rats but not in the 24- or 60-day-old animals. Serum testosterone was significantly reduced by 50% in the group of 14-day-old animals but not in the other age groups. Serum LH values were not significantly changed from control levels in any age group. Testicular content of Fe, Zn, Mn, and Cn were unaltered by procarbazine administration in any age group. Since serum LH and testicular cation content were not affected by procarbazine treatment, the significant decreases in serum and testicular testosterone in 14-day-old animals after procarbazine administration may indicate a direct age-dependent effect of procarbazine on Leydig cell function.

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.

Evidence suggesting that germ cells influence the bidirectional secretion of androgen binding protein by the seminiferous epithelium demonstrated by selective impairment of spermatogenesis with busulphan

Androgen binding protein (ABP) was measured in the serum, testes and epididymides of adult rats up to 105 days after the induction of reversible impairment of spermatogenesis by a single injection of busulphan. This treatment decreased testicular and epididymal weights within 7-21 days after treatment, reaching a minimum at 63 days with partial recovery by 105 days. The testicular and epididymal content of sperm was unchanged up to 42 days after busulphan administration, was reduced considerably at 63 days and thereafter increased towards control values. The serum and testicular concentrations of testosterone were normal at all times after treatment, even though serum LH levels were increased at 42 and 63 days. Serum levels of FSH were also increased at 43 and 63 days after treatment. A biphasic pattern in the serum levels of ABP was observed. Concentrations were low up to 43 days post treatment when only the early germ cell types were depleted from the seminiferous epithelium and when the testicular and epididymal contents of ABP were normal. Serum levels of ABP increased as the more mature germ cells were depleted in numbers and the testicular and epididymal contents of ABP declined. It is concluded that bidirectional secretion of ABP into the interstitium (serum) and into the seminiferous tubular lumen by Sertoli cells is influenced considerably by the population of germ cells that are present in the seminiferous epithelium.

A study of intercellular bridges during spermatogenesis in the rat

A morphological evaluation of intercellular bridges was undertaken during rat spermatogenesis. The dimensions and relationships of the bridges were shown to vary during different phases of spermatogenesis. Cellular divisions of spermatogonia and spermatocytes resulted in the partitioning of pre-existing bridges by complex structures termed bridge partitioning complexes, which are described in detail, as is the process whereby new bridges are formed. The structure of premeiotic bridges was generally consistent; however, during spermiogenesis, the structure of bridges and bridge contents were modified at specific phases of their development. The plasma membrane density associated with the cytoplasmic aspect of early step 1 spermatids separated into multiple dense bands that encircled the peripheral aspect of late step 1 spermatid bridges. By step 2 of spermiogenesis, these dense bands became associated with several cisternae of endoplasmic reticulum, which later coalesced into a single saccule that completely encircled the bridge structure by step 4. At steps 10-13 of spermiogenesis, the single saccule of endoplasmic reticulum vesiculated into many smaller cisternae. Also, filament-bounded densities (measuring 10-12 nm in diameter) appeared within the bridge channel. At step 17 of spermiogenesis, the filament-bounded densities were no longer apparent, but an anastomosing network of endoplasmic reticulum, often in the configuration of a sphere, occupied the entire central region of the bridge. In step 19 spermatids, the smooth endoplasmic reticulum within the bridge channel and the multiple cisternae lining the bridge density were gradually displaced. The subsurface density of bridges gradually lost its prominence. Some cytoplasmic lobes were connected by extremely narrow (approximately 22 nm) cytoplasmic channels. Similar-appearing channels were seen on the surface zone of cytoplasmic lobes or residual bodies, this observation suggesting that channels were sites of severence of bridges. Just prior to the separation or disengagement of the spermatid from the cytoplasmic lobe, selected bridges appeared to open to form large masses. After spermiation, residual bodies were not found joined by bridges; but from the size of some of the residual bodies, it was suspected that they were formed by coalescence of more than one cytoplasmic lobe. Freeze-fracture demonstrated few intramembranous particles on either the P or E face of the plasma membrane forming the bridge; this finding suggested bridge structures restricted free lateral movement of membrane constituents across the bridge.(ABSTRACT TRUNCATED AT 400 WORDS)

Actin localization in male germ cell intercellular bridges in the rat and ground squirrel and disruption of bridges by cytochalasin D

Filaments about 6-7 nm in diameter were seen associated with germ cell intercellular bridges in detergent-permeabilized cells treated with tannic acid. Approximately 40-50 filaments were present subjacent to the bridge density. Filaments encircled the bridge channel in a manner similar to contractile ring actin filaments of dividing cells. NBD-phallacidin and myosin S-1 subfragments were employed to demonstrate that the filaments observed at intercellular bridges are actin. Intratesticular injection of a single dose of cytochalasin D, a specific inhibitor of actin filaments, caused certain intercellular bridges of spermatids to open within 3 hr after injection, leading to the production of symplasts. During bridge opening, remnants of bridge densities were gradually incorporated into the lateral aspect of the plasma membrane of the symplast. Thus actin, present in bridge structures, appeared to participate in maintaining certain intercellular bridges. A model of intercellular bridge structure is presented.

Intratesticular injection as a method to assess the potential toxicity of various agents and to study mechanisms of normal spermatogenesis

To better understand, to optimize, and to validate the technique of intratesticular (i.t.) injection, several parameters related to i.t. injection were examined. Volumes exceeding 50 microliters could be injected i.t.; however, testes frequently became excessively turgid and backflow of injected fluids occurred. Thus, a volume of 50 microliters or less was deemed optimal for injection. To determine the rate of distribution of substances throughout the testis, trypan blue was injected i.t. near the caudal pole of the testis, and the movement of dye was monitored. Within 2 min, the dye had spread approximately 1 cm from the site of injection, and in 5 min it had spread twice that distance. In 2 h, the dye had become distributed throughout the testis except at its extreme cranial pole. Seminiferous tubules did not take up dye, indicating that the spread of dye was via peritubular lymphatics. Seminiferous tubule histology appeared virtually unaffected by i.t. injection, even at regions adjacent to the site of injection, when a sterile 26-gauge or smaller bore needle was utilized. To determine disappearance from the testis, radiolabeled inulin was injected i.t. Half time for absorption was achieved at 1.75 h. Potential vehicles were explored in which compounds with a variety of physical properties could be injected. Gum tragacanth, normal saline, ethylene glycol, dimethyl sulfoxide (DMSO) mixed 1:1 with normal saline, sesame oil, and propylene glycol were found to be suitable injection vehicles, whereas ethanol, dissolved in normal saline in concentrations as low as 0.5% was found unsuitable. To assess vehicle efficiency, various vehicles were utilized with a known testicular toxin (taxol) and injected into one testis, and the histology was compared with the contralateral testis injected with vehicle alone. All vehicles, found suitable above, allowed dispersion of taxol to influence areas distant from the site of injection. Intratesticular injection assesses the potential of agents to directly affect the testis, and systemic metabolism is avoided. Their rapid spread throughout the lymphatics of the testes allows seminiferous tubules to be exposed to agents in innocuous vehicles more rapidly and in higher concentration than is often possible when using systemic injections.

Attempted protection of spermatogenesis from single doses of gamma-irradiation in the androgen pretreated rat

Spermatogenic stem-cell survival after gamma-irradiation has been investigated in the adult Wistar rat. Single doses of 4.5 and 9 Gy gamma-rays were administered to the testes of rats who received arachis oil (0.1 ml/100 g body weight) or testosterone enanthate (240 micrograms/100 g body weight) subcutaneously three times weekly for 6 weeks prior to radiation and during the week in which the radiations were given. A mean percentage of regenerating seminiferous tubule cross-sections of 32.45% and 7.26% was found in the testes of androgen-pretreated rats at 8 weeks after 4.5 and 9 Gy, respectively. Similar values (33.4% and 6.2%) were obtained in arachis oil-pretreated controls. We therefore conclude that protection of rat spermatogenesis from single doses of gamma-rays cannot be achieved by androgen pretreatment.

Leydig cell function in the pubertal rat following local testicular irradiation

Dose- and time-response relationships were measured after irradiation of the pubertal rat testis with between 1 and 20 Gy of 300 kVp X-rays. The threshold dose for Leydig cell dysfunction was about 5 Gy. Dysfunction after higher doses was observed by 2 weeks post-irradiation as a dose-dependent decrease in serum testosterone (T) concentrations, and the levels were undetectable after 15 or 20 Gy. Despite the recovery of serum T by 24 and 36 weeks, dysfunction of the Leydig cell population was still observed as an increase in luteinizing hormone (LH) secretion (1.5 to 2-fold increase after 15 or 20 Gy at 24 weeks; 2 to 3-fold increase after 10 or 20 Gy at 36 weeks). The endocrine changes were probably due to the observed loss of Leydig cells following irradiation. These results indicate that the Leydig cells of pubertal rats are more radioresponsive than those of the adult.

Seminiferous epithelial function in the pubertal rat following local testicular irradiation

The dose- and time-related responses of the irradiated seminiferous epithelium in the pubertal rat have been investigated. The threshold dose for Sertoli cell dysfunction, as assessed by serum androgen binding protein (ABP) concentrations, was estimated to be 5 Gy. A significant reduction (to less than 50% of control levels) in serum ABP was observed at 8 weeks post-irradiation, with further reductions at later times (24 and 36 weeks). Serum follicle-stimulating hormone (FSH) was elevated to between 130 and 175% of control at only 2 weeks post-irradiation, but recovered with time. Normal FSH levels seemed to be related to recovery of spermatogenesis, as assessed by counts of regenerating tubule cross-sections. The results indicate that the clonogenic spermatogonia and Sertoli cells of the pubertal rat testis are less sensitive to radiation than those of the adult.

Dose and time related responses of the irradiated prepubertal rat testis. II. Seminiferous epithelial function

Dose-related effects of radiation upon the seminiferous epithelium were examined in the prepubertal rat. Marked damage to the spermatogenic cell populations was produced by doses of 5 Gy and above. As a result serum levels of FSH were increased, maximum changes being observed at 2 weeks, but levels remaining high even at 36 weeks after irradiation. Serum levels of androgen binding protein (ABP) were inversely related to serum FSH. Above a threshold dose of 5 Gy, serum ABP levels were reduced to between 30-50% of control values, possibly indicating damage to the Sertoli cells. Progression in the degree of testicular failure was indicated at 36 weeks after a dose of 15 Gy by further increases in serum gonadotrophins when compared to earlier times and by the absence of spermatogenesis.