Effects of guanethidine-induced sympathectomy on the spermatogenic and steroidogenic testicular functions of prepubertal to mature rats

Reproductive toxicity in male juvenile rats: Antagonistic effects between isolated agrochemicals and in binary or ternary combinations

The management of agrochemicals in Brazilian agriculture impacts global environmental sustainability and food security, since this country is one of the major agro-food exporters in the world. Acephate, carbendazim, and dithiocarbamates (DTCs) such as mancozeb, are among the most detected agrochemicals in Brazilian agro-food products, occurring in combination in several crops, especially in fruit cultures. The present study evaluated the impact of the exposure to isolated agrochemicals and all the combined possible mixtures (binary and ternary forms) on the reproductive parameters of male juvenile rats, known to be a vulnerable biological system and developmental window. Data were analyzed using Generalized Linear Models (GzLM), considering each agrochemical as an independent factor. The study revealed higher reproductive toxicity exerted by isolated agrochemicals when compared to the combined treatments, which exhibited mostly an antagonistic effect. Results suggest endocrine disruptive effects of each one separately on the weight of reproductive organs and testicular histomorphometry, besides changes in testicular SOD activity. The full factorial experimental design employed here allowed us to conclude that it is not possible to scale-up the effects of the isolated treatments to the mixtures, showing how difficult it is to know beforehand the response and cross-talk among the multiple physiological mechanisms disturbed by complex mixtures. Considering that food products are shared on a global scale and that some of these three agrochemicals have already been prohibited in EU countries, the consumption of some Brazilian products puts global human health at risk, that of children.

Prepubertal exposure to low doses of sodium arsenite impairs spermatogenesis and epididymal histophysiology in rats

For the first time, juvenile toxicity of inorganic arsenic (As) was investigated in male rats, focusing on reproductive effects. As is a metalloid naturally occurring in the environment, being the inorganic forms the most toxics. Contaminated drinking water and agricultural products are the main prospectors of intoxication for general population. In the present study, Wistar male rats (21 days old) were distributed into three groups (n = 10/group): control (received vehicle-filtered drinking water), As1 (received AsNaO₂ at 0.01 mg L^-1 ) and As2 (received AsNaO₂ at 10 mg L^-1 ). The animals were euthanized on PND 53. Testicular damages increased in As1 and As2 compared to control (ie, presence of vacuolization, acidophilic cells, and epithelium degeneration). Testicular interstitium of As1 and As2 presented fluid's increase and intense inflammatory infiltration. In the epididymis there was reduction of sperm amount in the lumen, besides epithelium areas presenting cribriform aspect in As1 and As2, exfoliation of cells in the light (in As1) and vacuoles (in As2). In epididymis interstitium, inflammatory infiltrates were observed in initial segment of As1 and As2. AsNaO₂ changed immunolabeling pattern for androgen receptor in epididymis of As2, although serum testosterone levels was statistically comparable to control. Mass spectrometry revealed higher As concentrations in testis and epididymis of As2 compared to As1 and Control. These results indicate compromise of spermatogenesis and epididymal histophysiology in AsNaO₂ -treated animals, possibly impairing sperm quality and fertility in long-term, even at low levels of exposure. Investigations about the reversibility of reproductive damages are necessary to better understand the mechanisms of As reproductive toxicity.

Perinatal exposure to insecticide fipronil: effects on the reproductive system in male rats

Fipronil is an insecticide widely used in agriculture, veterinary medicine and public health that has recently been listed as a potential endocrine disrupter. In the present study we evaluated the effects of perinatal exposure to fipronil during the period of sexual brain differentiation and its later repercussions on reproductive parameters in male rats. Pregnant rats were exposed (via gavage) to fipronil (0.03, 0.3 or 3 mg kg–1) from Gestational Day 15 until Postnatal Day 7. Fipronil exposure did not compromise the onset of puberty. In adulthood, there was no effect on organ weight or sperm production. Furthermore, there were no adverse effects on the number of Sertoli cells per seminiferous tubule, testicular and epididymal histomorphometry or histopathology or expression patterns of androgen receptor in the testis. Similarly, no changes were observed in the sexual behaviour or hormone levels. However, in rats exposed to fipronil, changes in sperm motility were observed, with a decrease in motile spermatozoa and an increase in non-mobile spermatozoa, which can compromise sperm quality in these rats. Perinatal exposure to fipronil has long-term effects on sperm parameters, and the epididymis can be a target organ. Additional studies should be undertaken to identify the mechanisms by which fipronil affects sperm motility.

Fish pollutants MeHg and Aroclor cause permanent structural damage in male gonads and kidneys after prepubertal exposure

This study investigated whether or not prepubertal exposure to the fish contaminants methylmercury (MeHg) and the polychlorinated bisphenol Aroclor in low doses interferes with the histomorphometry of the testes, epididymis, liver and kidneys in rats. Wistar male rats, 21 days old, were allocated into the following: control (n = 17, received corn oil), MeHg (n = 17, received MeHg at 0.5 mg/kg/day), Aroclor (n = 17, received Aroclor at 1.0 mg/kg/day), low mix (n = 18, received MeHg at 0.05 mg/kg/day and Aroclor at 0.1 mg/kg/day), high mix (n = 18, received MeHg at 0.5 mg/kg/day and Aroclor at 1.0 mg/kg/day). Dosing continued from post natal day (PND) 23 to 53, by gavage. Euthanasia was performed on PND 53; or, after an interval of 62 days without exposure to chemicals, on PND 115. The degree of maturation of the seminiferous epithelium was delayed in chemical-exposed groups and testicular interstitial oedema was observed at adulthood. The pattern of male gonad organization was changed in the Aroclor group on PND 53 and in all treated groups at adulthood. The animals from Aroclor, low mix and high mix groups showed a reduction in the number of Sertoli cells. Histological evidence of renal injury was observed in all chemical-exposed groups in both ages. A probable target for MeHg and Aroclor in the reproductive system was Sertoli cells, in which possible dysfunctions could be linked to the other testicular alterations. Curiously, the main deleterious effects were late outcomes, along with the absence of synergistic interaction of MeHg and Aroclor in the parameters investigated. In conclusion, fish pollutants MeHg and Aroclor caused permanent structural damage in male gonads and kidneys after prepubertal exposure, without showing clear chemical interactions.

Short- and long-term reproductive effects of prenatal and lactational growth restriction caused by maternal diabetes in male rats

BACKGROUND

A suboptimal intrauterine environment may have a detrimental effect on gonadal development and thereby increases the risk for reproductive disorders and infertility in adult life. Here, we used uncontrolled maternal diabetes as a model to provoke pre- and perinatal growth restriction and evaluate the sexual development of rat male offspring.

METHODS

Maternal diabetes was induced in the dams through administration of a single i.v. dose of 40 mg/kg streptozotocin, 7 days before mating. Female rats presenting glycemic levels above 200 mg/dL after the induction were selected for the experiment. The male offspring was analyzed at different phases of sexual development, i.e., peripuberty, postpuberty and adulthood.

RESULTS

Body weight and blood glucose levels of pups, on the third postnatal day, were lower in the offspring of diabetic dams compared to controls. Maternal diabetes also provoked delayed testicular descent and preputial separation. In the offspring of diabetic dams the weight of reproductive organs at 40, 60 and 90 days-old was lower, as well as sperm reserves and sperm transit time through the epididymis. However the plasma testosterone levels were not different among experimental groups.

CONCLUSIONS

It is difficult to isolate the effects directly from diabetes and those from IUGR. Although the exposure to hyperglycemic environment during prenatal life and lactation delayed the onset of puberty in male rats, the IUGR, in the studied model, did not influenced the structural organization of the male gonads of the offspring at any point during sexual development. However the decrease in sperm reserves in epididymal cauda and the acceleration in sperm transit time in this portion of epididymis may lead to an impairment of sperm quality and fertility potential in these animals. Additional studies are needed in attempt to investigate the fertility of animals with intrauterine growth restriction by maternal diabetes and possible multigenerational effects.

In utero protein restriction causes growth delay and alters sperm parameters in adult male rats

BACKGROUND

Recent studies have supported the concept of "fetal programming" which suggests that during the intrauterine development the fetus may be programmed to develop diseases in adulthood. The possible effects of in utero protein restriction on sexual development of rat male offspring were evaluated in the present study.

METHODS

Pregnant Wistar rats were divided into two experimental groups: one group treated with standard chow (SC, n = 8, 17% protein) and the other group treated with hypoproteic chow (HC, n = 10, 6% protein) throughout gestation. After gestation the two experimental groups received standard chow. To evaluate the possible late reproductive effects of in utero protein restriction, the male offspring of both groups were assessed at different phases of sexual development: prepubertal (30 days old); peripubertal (60 days old); adult (90 days old). Student's t-test and Mann-Whitney test were utilized. Differences were considered significant when p < 0.05.

RESULTS

We found that in utero protein restriction reduced the body weight of male pups on the first postnatal day and during the different sexual development phases (prepubertal, peripubertal and adult). During adulthood, Sertoli cell number, sperm motility and sperm counts in the testis and epididymal cauda were also reduced in HC. Furthermore, the numbers of sperm presenting morphological abnormalities and cytoplasmic drop retention were higher in HC.

CONCLUSIONS

In conclusion, in utero protein restriction, under these experimental conditions, causes growth delay and alters male reproductive-system programming in rats, suggesting impairment of sperm quality in adulthood.

Effects of methylmercury on male reproductive functions in Wistar rats

In this study we investigated the effects of subacute exposure to methylmercury (MeHg) on male reproductive functions in rats by means of determination of alterations in structural and functional parameters. Adult male Wistar rats received 0, 0.5, 1.0 or 3.0 mg/kg/body weight/day orally, daily MeHg for 14 days. Sperm motility, the relative sperm count and transit time in the caput/corpus epididymis, were all reduced at all doses. The lowest dose increased the number of sperm head abnormalities; daily sperm production was elevated at the intermediate dose; while at the highest dose there was a decrease in serum testosterone levels and a rise in mercury (Hg) content in reproductive organs, liver and kidneys. In conclusion, MeHg exposure produced damages on male reproductive functions which may be attributed, at least in part, to the reduction in serum testosterone levels. These consequences could potentially result in infertility in rats.

Effects of gestational and lactational fenvalerate exposure on immune and reproductive systems of male rats

The aim of this study was to determine the consequent reproductive developmental and immunotoxic effects due to exposure to fenvalerate during pregnancy and lactation in male offspring of maternal-treated rats. Pregnant rats were treated daily by oral gavage with 40 or 80 mg/kg of fenvalerate or corn oil (vehicle, control), from d 12 of pregnancy to d 21 of lactation. Immune and reproductive developmental effects were assessed in male offspring at postnatal days (PND) 40 (peripuberty), 60 (postpuberty), and 90 (sexual maturity). Treatment with the higher dose (80 mg/kg) resulted in convulsive behavior, hyperexcitability, and mortality in 45% of the dams. Fenvalerate was detected in the fetus due to placental transfer, as well as in pups due to breast-milk ingestion, persisting in male offspring until PND 40 even though pesticide treatment was terminated on PND 20. However, fenvalerate did not produce marked alterations in age of testicular descent to the scrotum and prepucial separation, parameters indicative of puberty initiation. In contrast, at puberty, there was a reduction in testicular weight and sperm production in male offspring of maternal-treated rats. At adulthood, the sperm counts and fertility did not differ between control and treated groups. Testosterone levels were not changed at any time during reproductive development. Similarly, no apparent exposure-related effects were detected in the histological structures of the lymphohematopoietic system. Data indicate that fenvalerate, in this experimental model, interfered with initial development of the male reproductive system, but that these effects on sperm production or fertility did not persist into adulthood. There was no apparent evidence that fenvalerate altered testosterone levels or produced a disruption in male endocrine functions.

Effects of altered epididymal sperm transit time on sperm quality

The epididymal sperm transit time seems to have an important role in the process of sperm maturation, and it seems that alterations to the transit can harm the process. The aim of the present work was to evaluate the influence of altered sperm transit time through the epididymis on sperm parameters and fertility of rats, as well as the role of testosterone in the alterations. Sprague-Dawley adult male rats were randomly assigned to four different groups and were treated for 12 days: (i) 10 microg/rat/day DES, to accelerate the transit; (ii) 6.25 mg/kg/day guanethidine sulphate, to delay the transit; (iii) same treatment as group 1, plus androgen supplementation; (iv) control animals received the vehicles. Guanethidine treatment delayed the sperm transit time through the epididymal cauda, provoking increased sperm reserves in this region. Animals exposed to DES showed an acceleration of sperm transit time in the epididymis, and consequently decreased sperm density in both epididymal regions, the caput-corpus and cauda, and diminished sperm motility. In both cases sperm production was not altered. Testosterone supplementation was able to restore the transit time to values close to normality, as they were higher than in the control rats. The same occurred in relation to sperm motility. Rats exposed to DES presented lower fertility after in utero artificial insemination using sperm collected from the proximal cauda epididymis. Therefore, it was concluded that the acceleration of rat sperm transit time appeared to harm normal sperm maturation, thus decreasing sperm quality and fertility capacity, in an androgen-dependent way.

In the adult male rhesus monkey (Macaca mulatta), unilateral orchidectomy in the face of unchanging gonadotropin stimulation results in partial compensation of testosterone secretion by the remaining testis

This study examined, in adult monkeys, the role that gonadotropin-independent mechanisms play in compensation of testosterone (T) secretion by the testis that remains after unilateral orchidectomy (UO). We employed a model (testicular clamp), in which endogenous gonadotropin secretion was abolished with a GnRH receptor antagonist, and the gonadotropin drive to the testes was concomitantly replaced with an invariant iv pulsatile infusion of recombinant human LH and FSH (1-min pulse every 2.5 h: LH, 0.08-0.12 IU/kg.pulse; FSH, 0.12-0.32 IU/kg.pulse) that provided the Leydig cells with a physiological stimulus. Within 5 h of UO (n = 5), circulating T concentrations had declined to 43% of pre-UO levels. By d 4, however, loss of the first testis was partially compensated, as reflected by the finding that circulating T had reached a plateau of 67% of the pre-UO level, where it remained for the duration of the study (39 d). That the recovery in circulating T was the result of increased T secretion by the remaining testis was suggested by the finding that the pulsatile pattern and decay of T during the intergonadotropin pulse interval before and after UO were indistinguishable. Interestingly, inhibin B production by the remaining testis also showed a delayed, albeit, minor, compensation (13% on d 10-11; P > 0.05) after loss of the first testis. These results suggest that compensation in T production by the remaining testis after UO in adult monkeys may be achieved in part by a gonadotropin-independent mechanism that probably involves direct neural inputs to the primate testis.