Circulating activin A during equine gestation and immunolocalization of its receptors system in utero-placental tissues and fetal gonads

Although equine gestation is unique from the standpoint of fetal gonadal enlargement and regression, the activator of this process is still unknown. The present study aimed to show a possible role of activin during equine gestation. In the first experiment, weekly plasma samples from six pregnant mares were used to measure activin A. In the second experiment, eight pregnant mares carrying female (gestational days 110, 140, 180, and 270) and male fetuses (gestational days 120, 180, 225, and 314) were used for immunohistochemistry of activin receptors (IA, IB, IIA, IIB), and their intracellular mediators (Smad2, Smad3, Smad4). Activin A levels in maternal circulation remained low until fourth weeks of gestation, thereafter, started to increase, and peaked first at 11 weeks of gestation. The second significant peak was observed on the day of parturition. Activin receptors type IA, IB, IIA, and IIB were immunostained in interstitial and germ cells of fetal ovaries and testes along with utero-placental tissues. Smad2, Smad3, and Smad4 were also immunolocalized in all these organs. These results demonstrated the activin-producing capacity of utero-placental tissues, and also evidenced the existence of activin receptors and functional signaling molecules in these organs. The first increment in circulating activin A in maternal circulation coinciding with the timing of initiation of fetal gonadal enlargement suggests that activin from the utero-placental tissues may have a stimulatory role in fetal gonad enlargement and utero-placental development in mares, whereas the second peak could be important to follicular development in the maternal ovary for foal heat.

Influence of exercise and emotional stresses on secretion of prolactin and growth hormone in Thoroughbred horses

The secretion of prolactin and growth hormone in response to exercise and emotional stresses was investigated in Thoroughbreds. Two experiments were performed: one with loading of only exercise stress and one with simultaneous loading of exercise and emotional stresses. Exercise stress was loaded in 4 steps using a treadmill for horses: pre-exercise period (5 min), walking period (6.5 min), galloping period (3 min), and cooling down period (10 min). Emotional stress was loaded by showing a loud video of an audience at a racetrack during the walking period. The results clearly demonstrated that exercise stress rapidly increased the secretion of prolactin and growth hormone and that secretion of them persisted for a specific period after the exercise. In addition, emotional stress promoted prolactin secretion.

Changes in luteinizing hormone pulse frequency and prolactin levels in bitches in response to estrus induction by cabergoline-its cases where it is delayed to induce estrus

The effect of estrus induction by cabergoline on gonadotropin and steroid hormone responses was examined in anestrous bitches. Eleven beagles were used in the study; seven were included in the estrus induction group and four were included in the spontaneous estrus group. Cabergoline was orally administered to the estrus induction group at 5 µg/kg once daily for four weeks, or until hemorrhagic discharge was detected. The inter-estrus interval in the estrus induction group was significantly shorter than the previous estrus interval. Bitches that showed proestrus within four weeks of treatment showed increased luteinizing hormone (LH) pulse frequency and, subsequently, increased estradiol (E₂) levels. Prolactin (PRL) levels declined promptly after treatment, except in one bitch that did not show proestrus during the cabergoline treatment period. There was a significant correlation between the time to proestrus induction and the reduction in PRL levels. A positive correlation was found between the LH levels two weeks after cabergoline administration and PRL reduction. This study demonstrates that an abrupt reduction in PRL is likely to be important for initiation of estrus in bitches. A reduction in PRL indirectly leads to an increase in LH pulse frequency, which regulates follicular development in bitches. However, if the period from the end of the previous estrus to the cabergoline treatment is short, it may take some time to show proestrus without increasing E₂ levels, even if the LH level increases after cabergoline administration.

Expression of activin receptors in the equine uteroplacental tissue: an immunohistochemical analysis

Activin is secreted from equine uterine glands and plays important roles in establishment and maintenance of pregnancy in mares. This study aimed to localize activin receptors (ActRs) IA/B and IIA/B using immunohistochemistry in the uteroplacental tissues of seven pregnant Thoroughbred mares. At the time of tissue collection, the mares were at the following days of pregnancy: 88, 120, 161, 269, 290, 313, and 335 days. We fixed the uteroplacental tissues in 4% paraformaldehyde and obtained serial sections that were subsequently stained for analysis. All four isoforms of ActR were expressed in the uteroplacental tissues, including the endometrial epithelium, uterine glands, trophoblasts, and myometrium, throughout pregnancy. Our results suggested the potential role of activin in the uteroplacental tissues.

Circulating gonadotropins and testicular hormones during sexual maturation and annual changes in male bottlenose dolphins (Tursiops truncatus)

To reveal the reproductive biology in male bottlenose dolphins (Tursiops truncatus), circulating gonadotropins (follicle stimulating hormone [FSH] and luteinizing hormone [LH]) and testicular hormones (testosterone and inhibin) were monitored for 8−12 years in 2 captive bottlenose dolphins (Mars and Regulus). During the study period, Mars was undergoing sexual maturation, whereas Regulus was already mature at the beginning of the study. Assuming that Mars had reached sexual maturity when the significant increase in circulating testosterone levels was observed, serum concentration of inhibin was higher in the sexually immature stage than in the mature stage, whereas the serum concentration of FSH was higher in the sexually mature stage than in the immature stage. No difference was observed in the LH levels between pre- and post-sexual maturation. There was a significant increase in serum concentration of testosterone during spring in both animals. These results suggest that the mechanism responsible for regulating FSH secretion by inhibin functions during the sexually immature stage in this species.

Evaluation of the chemiluminescent enzyme immunoassay system for the measurement of testosterone in the serum and whole blood of stallions

Testosterone (T) concentration is a useful indicator of reproductive function in male animals. However, T concentration is not usually measured in veterinary clinics, partly due to the unavailability of reliable and rapid assays for animal samples. In this study, a rapid chemiluminescent enzyme immunoassay system (CLEIA system) that was developed for the measurement of T concentration in humans use was validated for stallion blood samples. First, serum T concentrations were measured using the CLEIA system and compared with those measured by a fluoroimmunoassay that has been validated for use in stallions. The serum T concentrations measured by the two methods were highly correlated (r = 0.9865, n = 56). Second, to validate the use of whole blood as assay samples, T concentrations in whole blood and in the serum were measured by the CLEIA system. T concentrations in both samples were highly correlated (r = 0.9665, n = 64). Finally, to evaluate the practical value of the CLEIA system in clinical settings, T concentrations were measured in three stallions with reproductive abnormalities after the administration of human chorionic gonadotropin (hCG). Two stallions with small or absent testes in the scrotum showed an increase in T production in response to hCG administration and one stallion with seminoma did not. In conclusion, the CLEIA system was found to be a rapid and reliable tool for measuring T concentrations in stallions and may improve reproductive management in clinical settings and in breeding studs.

4-Nitrophenol (PNP) inhibits the expression of estrogen receptor β and disrupts steroidogenesis during the ovarian development in female rats

4-nitrophenol (PNP), isolated from diesel exhaust particles, has estrogenic and anti-androgenic activities, and affects the hypothalamus-pituitary-gonad axis in male rats. However, the effect of PNP on the reproduction of the female rats is still unknown. The aim of the study was to investigate the effect of neonatal PNP exposure on the ovarian function of female rats. The neonatal female rats were exposed to PNP (10 mg/kg, subcutaneously injection), the ovary and serum samples were collected at postnatal day (PND) 7, 14 and 21. The results showed that the ratio of primordial and primary follicles increased whereas the ratio of antral follicles decreased in the PNP treated ovaries at PND21. Even though no abnormality was observed in cyclicity, there was a significantly delayed timing of vaginal opening in PNP treated rats. The ovarian expression of steroidogenic enzymes including StAR, P450scc, P450c17 and P450arom increased at PND14 in the PNP treated rats compared with the control rats. In consistent with the gene expression, the concentration of estradiol-17β showed the similar pattern. However, PNP exposure failed to cause any significant change in the expression of steroidogenic enzymes in cultured neonatal ovaries. Furthermore, PNP suppressed the expression of estrogen receptor β (ERβ), but not estrogen receptor α (ERα), in cultured ovaries or developmental ovaries. These results suggested that PNP might directly affect the expression of ERβ in the rat ovaries, resulting in the disrupted steroidogenesis during ovarian development and the delayed puberty.

Seasonal expression of P450arom and estrogen receptors in scented glands of muskrats (Ondatra zibethicus)

Male muskrats have one pair of scented glands that grow and involute annually. To investigate the annual changes in the scented gland, we measured the expressions of aromatase cytochrome P-450 (P450arom) and estrogen receptors (ERs) in the scented glands. P450arom was expressed in glandular cells and epithelial cells in the scented glands during the breeding season, and only in glandular cells during the nonbreeding season. ERα and ERβ were also detected in different types of cells in the scented gland during the breeding and nonbreeding seasons. Both mRNA and protein levels of P450arom, ERα, and ERβ were higher in the scented glandular tissues during the breeding season than those during the nonbreeding season. In addition, small RNA sequencing showed that the predicted targets of the significantly changed microRNAs might be the genes encoding P450arom and ERs. In conclusion, the seasonal changes in the expression of P450arom and ERs may be involved in the regulation of scented gland functions.

Seasonal expressions of follicle-stimulating hormone receptor and luteinizing hormone receptor in the scented gland of the male muskrat (Ondatra zibethicus)

Accumulating evidence has shown that follicle-stimulating hormone (FSH) and luteinizing hormone (LH) may influence the functions of nongonadal tissues in addition to their classic target gonads. Our previous studies revealed that the scented glands of male muskrats expressed prolactin receptor, steroidogenic enzymes, and inhibin/activin subunits. To further seek the evidence of the activities of pituitary gonadotropins in scented glands, we investigated the seasonal expression patterns of FSH receptor (FSHR) and LH/choriogonadotropin receptor (LHCGR). The weight and size of scented glands during the breeding season were significantly higher than those during the nonbreeding season. Immunohistochemical studies showed that FSHR was present in the serous cells of scented glands, whereas LHCGR was present in the interstitial cells. The protein and mRNA expression levels of FSHR and LHCGR were significantly higher in the scented glands during the breeding season than those during the nonbreeding season. Importantly, the levels of circulating FSH and LH were remarkably higher during the breeding season. Taken together, these results suggested that gonadotropins may affect the function of muskrat scented gland via the locally expressed receptors in a season-dependent manner.

Annual ovarian activity monitored by the noninvasive measurement of fecal concentrations of progesterone and 17β-estradiol metabolites in rusa deer (Rusa timorensis)

To clarify the reproductive cycle of female Rusa deer (Rusa timorensis), the fecal concentrations of progesterone and 17β-estradiol metabolites were measured. Fecal samples were collected on a weekly basis for one year (between October, 2012 and September, 2013) from five healthy adult hinds in Thailand. At the beginning of the study, three hinds were pregnant. Two hinds delivered one healthy offspring, and one hind delivered a stillborn calf. The mating period of Rusa hinds in Thailand is from November to April. In pregnant hinds, fecal progesterone metabolite concentration was high in late pregnancy and abruptly declined to the baseline around parturition, suggesting that the placenta secretes a large amount of progesterone. Fecal 17β-estradiol metabolite concentration remained elevated around the day of parturition. Both concentrations of fecal progesterone and 17β-estradiol metabolites in non-lactating hinds were significantly higher than those in lactating hinds, indicating that ovarian activity of lactating hinds is suppressed by the suckling stimulus of fawn during lactation. The present study demonstrated that monitoring of fecal steroid hormones is useful method for assessing ovarian function in this species.

Effects of a single use of the GnRH analog buserelin on the induction of ovulation and endocrine profiles in heavy draft mares

We observed structural changes in the follicles and uterus of heavy draft mares during estrus and examined the effect of a single injection of the gonadotropin-releasing hormone analog buserelin on ovulation and endocrine profiles. Twenty-two heavy draft mares were divided into a buserelin-treated group (n=8) and a control group (n=14). Mares were given an intramuscular injection of 40 µg buserelin when they presented signs of estrus to a teaser stallion, had ≥45 mm diameter follicles, and presented decreased uterine edema compared with the previous examination. The follicles and uterus were monitored using transrectal ultrasound imaging and measurement of blood levels of luteinizing hormone (LH), follicle-stimulating hormone (FSH), progesterone, and estradiol-17β. The ovulation rates within 48 hr was significantly higher in the treated group (100%, 8/8) than in the control group (57.1%, 8/14; P=0.051). The mean ± SEM time before confirmation of ovulation was 29 ± 9 hr for the treated group and 59 ± 7 hr for the control group. There were no significant differences in mating frequency, double ovulation rate, or fertility rate between the two groups. One to two days after administering buserelin, LH and FSH temporarily increased, and in the control group, LH was high during ovulation, whereas FSH temporarily increased with the growth of the follicle. These results indicate that a single injection of 40 µg buserelin when follicles are at least 45 mm in diameter and uterine edema is decreased is effective for inducing ovulation.

Bisphenol a Inhibits Testicular Functions and Increases Luteinizing Hormone Secretion in Adult Male Rats

Effects of a xenoblotic estrogen, bisphenol A (BPA), on reproductive functions were investigated using adult male rats. BPA was dissolved into sesame oil and injected sc every day (1 mg/rat) for 14 days. Animals were killed by decapitation after the final administration of BPA, and the trunk blood, pituitary, and testes were collected. Plasma concentrations of prolactin were dramatically Increased and pituitary contents of prolactin were slightly increased in the BPA group compared to the control group. Plasma concentrations of testosterone were decreased and plasma concentrations of LH were increased in BPA-treated rats compared to control rats. Testicular contents of inhibin were decreased in BPA-treated rats compared to control rats, although plasma concentrations of inhibin were not changed after administration of BPA. The testicular response to hCG for progesterone and testosterone release was decreased in BPA-treated rats. Administration of BPA did not change the pituitary response to luteinizing hormone-releasing hormone (LH-RH) in castrated male rats treated with testosterone. Male sexual behavior also was not changed as a result of BPA treatment. These results suggest that BPA directly inhibits testicular functions and the increased level of plasma LH is probably due to a reduction in the negative feedback regulation by testosterone. The testis is probably a more sensitive site for BPA action than the hypothalamus–pitultary axis.

Effects of Daily Exposure to Saccharin and Sucrose on Testicular Biologic Functions in Mice

Saccharin sodium consumption is considered safe and beneficial, owing to its very intense sweetness without any associated calories, but supporting scientific data remain sparse and controversial. Herein, we demonstrate that dose-response relationships existed with regard to administration of saccharin or sucrose to mice for 35 days, and this association involved testis-expressed sweet-tasting molecules (taste receptor type 1 subunit 3 [T1R3]; G protein alpha-gustducin [Galpha]). Mouse body weights and testis weights in middle- and low-dose saccharin-treated groups were increased with up-expressions of molecules involved in testicular sweet taste and steroidogenic (middle saccharin: steroidogenic acute regulatory protein [StAR]; P450 cholesterol side-chain cleavage enzyme [CYP11A1]; 17-alpha-hydroxylase/C17,20-lyase [CYP17A1]; low saccharin: StAR). Moreover, a high-dose saccharin-related decline in reproductive hormone levels and injuries to testis and sperm were observed to be associated with suppression of testicular T1R3 and Galpha, as well as steroidogenic-related factors (StAR; 3-beta-hydroxysteroid dehydrogenase [3-beta-HSD]; CYP11A1; CYP17A1; 17-beta-hydroxysteroid dehydrogenase [17-beta-HSD]), and activation of cleaved caspase-3. However, abnormalities of the testis and sperm in high- and middle-dose sucrose-exposed mice were related to the increased-cleaved caspase-3, but independent of T1R3 and/or Galpha. Collectively, our results clearly suggest that saccharin-induced physiologic effects on testis are associated with testicular T1R3 and Galpha, which differed from sucrose. We hence call for a reassessment of the excessive use of sweeteners in daily life, especially artificial ones, considering their potential side effects.

PATHFAST, a novel chemiluminescent enzyme immunoassay for measuring estradiol in equine whole blood and serum

A novel chemiluminescent enzyme immunoassay system, PATHFAST, for the measurement of estradiol in horses was evaluated. The concentrations of estradiol in the whole blood and serum of mares were measured using PATHFAST and the estradiol concentrations measured by PATHFAST were compared with those measured by a time-resolved fluoro-immunoassay (FIA). To monitor physiological changes, serum estradiol concentrations in mares were measured using PATHFAST throughout the gestation period. The serum estradiol concentrations correlated highly with those in whole blood samples. The serum concentrations of estradiol measured by PATHFAST also correlated well with FIA. Circulating estradiol increased during mid-gestation and high levels of serum estradiol were maintained in late gestation, followed by an abrupt decline to term. These results demonstrate the utility of PATHFAST in equine clinics as an accurate diagnostic tool for the rapid assay of estradiol within 26 min using unextracted whole blood.

Evidence for a PGF2α auto-amplification system in the endometrium in mares

In mares, prostaglandin F2α (PGF2α) secreted from the endometrium is a major luteolysin. Some domestic animals have an auto-amplification system in which PGF2α can stimulate its own production. Here, we investigated whether this is also the case in mares. In an in vivo study, mares at the mid-luteal phase (days 6-8 of estrous cycle) were injected i.m. with cloprostenol (250 µg) and blood samples were collected at fixed intervals until 72 h after treatment. Progesterone (P4) concentrations started decreasing 45 min after the injection and continued to decrease up to 24 h (P < 0.05). In turn, 13,14-dihydro-15-keto-PGF2α (PGFM) metabolite started to increase 4h after an injection and continued to increase up to 72 h (P < 0.05). PGF receptor (PTGFR) mRNA expression in the endometrium was significantly higher in the late luteal phase than in the early and regressed luteal phases (P < 0.05). In vitro, PGF2α significantly stimulated (P < 0.05) PGF2α production by endometrial tissues and endometrial epithelial and stromal cells and significantly increased (P < 0.05) the mRNA expression of prostaglandin-endoperoxide synthase-2 (PTGS2), an enzyme involved in PGF2α synthesis in endometrial cell. These findings strongly suggest the existence of an endometrial PGF2α auto-amplification system in mares.

Promoting effects of an extended photoperiod treatment on the condition of hair coats and gonadal function in Thoroughbred weanlings

The effects of an extended photoperiod (EP) treatment (14.5 hr light, 9.5 hr dark) on Thoroughbred colts and fillies from December 25 at 7-9 months old to the following May at 12-14 months old on coat condition and gonadal functions were investigated. Coat condition was evaluated in April. The colts and fillies in the EP treatment group changed from winter to summer coats (molting of winter coats), whereas those in the control group did not. To determine the day of first ovulation, the plasma concentrations of progesterone were measured once a month in fillies. The day of first ovulation was advanced in the EP treatment fillies compared with the control fillies. The present study clearly demonstrated that the EP treatment advanced the molting of winter coats and advanced ovulation in fillies, even in weanlings.

Different effects of an extended photoperiod treatment on growth, gonadal function, and condition of hair coats in Thoroughbred yearlings reared under different climate conditions

One- to two-year-old Thoroughbred colts and fillies being reared in Miyazaki (warm climate) and Hidaka (cold climate), Japan, were administered extended photoperiod (EP) treatment between December 20 and the following April 10, and its effect on growth, endocrine changes, gonadal activation, and hair coat condition was investigated. In colts reared in Miyazaki, no effect of EP treatment was noted on the growth indices, including body weight (BW), height at withers (HW), girth, and cannon circumference (CC), whereas the BWs and CCs of fillies were significantly higher in the EP treatment group than the control. In Hidaka, the BWs and HWs of colts and HWs of fillies were significantly higher in the EP treatment group. Gonadal activation characterized by an increase in circulating hormone concentrations was earlier in the EP treatment group for fillies reared in Miyazaki [luteinizing hormone (LH), follicle-stimulating hormone (FSH), progesterone (P4), and estradiol-17β (E2)] and in colts (LH, testosterone, and E2) and fillies (LH, FSH, P4, and E2) reared in Hidaka. Regardless of sex and climate, prolactin was significantly higher in the EP treatment group, whereas insulin-like growth factor (IGF-I) was not. Initial ovulation occurred before April in more of the EP treatment group than the control regardless of the climate. Molting of the hair coat, examined in March, was advanced in the EP treatment group regardless of sex and climate. These results suggest that EP treatment may promote growth and gonadal activation in fillies reared in Miyazaki and in colts and fillies reared in Hidaka and that the effect may be mediated by prolactin.

The effect of phytosterol protects rats against 4-nitrophenol-induced liver damage

We investigated the effect of phytosterol (PS) in regard to liver damage induced by 4-nitrophenol (PNP). Twenty rats were randomly divided into four groups (Control, PS, PNP, and PNP+PS). The PS and PNP+PS groups were pretreated with PS for one week. The PNP and PNP+PS groups were injected subcutaneously with PNP for 28 days. The control group received a basal diet and was injected with vehicle alone. Treatment with PS prevented the elevation of the total bilirubin levels, as well as an increase in serum alkaline transaminase and aspartate transaminase, which are typically caused by PNP-induced liver damage. Histopathologically showed that liver damage was significantly mitigated by PS treatment. However, there was no significant change in antioxidant enzyme activities, and the Nrf2-antioxidant system was not activated after treatment with PS. These results suggest that PS could mitigate liver damage induced by PNP, but does not enhance antioxidant capacity.

Embryonic sex steroid hormones accumulate in the eggshell of loggerhead sea turtle (Caretta caretta)

Steroids hormones such as estradiol-17β (E2) and testosterone (T) are involved in gonadal differentiation of oviparous animals with temperature-dependent sex determination (TSD), and are greatly distributed. This hypothesizes that these embryonic steroid hormones probably accumulate in the eggshell throughout blood or/and chorioallantoic fluid in sea turtle species with TSD, producing females at higher temperature. To demonstrate this hypothesis, concentrations of E2 and T in the blood plasma from the hatchling loggerhead sea turtle (Caretta caretta) and in their eggshells were measured by radioimmunoassay. In the present study we propose that both concentrations of E2 and T in the blood plasma are correlated with amounts of these sex steroids in the eggshell. Moreover, contents of E2 in the eggshell showed a significant positive correlation with mean incubation temperatures during a thermosensitive period in the experimental nests, whereas T contents in the eggshell did not. Taken together, these findings indicated that embryonic E2 and T that accumulated in the eggshell can be extracted and measured. Furthermore, the present study suggested that contents of E2 in the eggshell may differ between male and female, and monitoring of these steroids is a useful method to identify the sex of loggerhead sea turtle hatchling.

Effects of sulpiride and ethylene glycol monomethyl ether on endometrial carcinogenicity in Donryu rats

Sulpiride and ethylene glycol monomethyl ether (EGME) are known ovarian toxicants that stimulate prolactin (PRL) secretion, resulting in hypertrophy of the corpora lutea and increased progesterone (P4) production. The purpose of the present study was to investigate how the PRL stimulatory agents affected uterine carcinogenesis and to clarify the effects of PRL on endometrial adenocarcinoma progression in rats. Ten-week-old female Donryu rats were treated once with N-ethyl-N'-nitro-N-nitrosoguanidine (20 mg kg(-1) ), followed by treatment with sulpiride (200 ppm) or EGME (1250 ppm) from 11 weeks of age to 12 months of age. Sulpiride treatment inhibited the incidence of uterine adenocarcinoma and precancerous lesions of atypical endometrial hyperplasia, whereas EGME had no effect on uterine carcinogenesis. Sulpiride markedly prevented the onset of persistent estrus throughout the study period, and EGME delayed and inhibited the onset of persistent estrus. Moreover, sulpiride-treated animals showed high PRL and P4 serum levels without changes in the levels of estradiol-17β, low uterine weights and histological luteal cell hypertrophy. EGME did not affect serum PRL and P4 levels. These results suggest that the prolonged low estradiol-17β to P4 ratio accompanied by persistent estrous cycle abnormalities secondary to the luteal stimulatory effects of PRL may explain the inhibitory effects of sulpiride on uterine carcinogenesis in rats. Copyright © 2015 John Wiley & Sons, Ltd.

Effects of an extended photoperiod on gonadal function and condition of hair coats in Thoroughbred colts and fillies

The effects of an extended photoperiod (EP) in Thoroughbreds colts and fillies from winter at one year old to spring at two years old on the gonadal functions, coat condition, and endocrine changes were investigated. Sixty-two Thoroughbreds (31 colts and 31 fillies) reared in the Hidaka Training and Research Center (Hidaka), Japan Racing Association were used. Thirty of them (15 colts and 15 fillies) were reared under EP conditions from December 20 to April 10, and the remaining 32 horses were reared under natural light alone as a control group. For EP, a 100-watt white bulb was set near the ceilings of stalls, and lighting conditions of 14.5-hr light and 9.5-hr dark periods were established. Blood was collected from the jugular vein once a month from October at one year old to February at two years old in both colts and fillies, and then twice a month in colts and weekly in fillies after March, and the coat condition was evaluated in January and April in 56 horses. To investigate endocrine changes, the plasma concentrations of prolactin, luteinizing hormone (LH), follicle-stimulating hormone (FSH), immunoreactive (ir-) inhibin, testosterone, estradiol-17β and progesterone were measured. No significant difference was noted in the coat condition between the two groups in January, but they changed from winter to summer coats (molting of winter coats) in April in the EP group compared with the control group. Regarding endocrine changes, the plasma concentrations of prolactin, FSH, ir-inhibin and testosterone were significantly higher in the EP colts than in the control group from January to April. The plasma concentrations of LH tended to rise in the EP colts from January to April compared with the control group. In the EP fillies, the plasma concentrations of prolactin, LH, ir-inhibin, estradiol-17β and progesterone were significantly higher during January and April, but a significantly high level of FSH was noted in the control than EP group in January. The ovulation day was advanced in the EP fillies compared with the control group. The present study clearly demonstrated that EP treatment during rearing advanced the molting of winter coats in both colts and fillies. These results suggested to be due to the action of prolactin being increased by EP treatment. In addition, EP treatment stimulated the hypothalamus-pituitary-gonadal axis even in yearlings, and advanced ovulation in fillies. Since EP treatment-induced changes in the yearlings were within the physiological range, and the method is safe and simple, EP treatment may be an effective technique in horse husbandry.

Comparison of growth and endocrine changes in Thoroughbred colts and fillies reared under different climate conditions

Development and endocrine changes in Thoroughbreds colts and fillies were compared between those reared at two facilities of the Japan Racing Association, the Hidaka Training and Research Center (Hidaka) and Miyazaki Yearling Training Farm (Miyazaki). Thoroughbred colts and fillies born in Japan between 2003 and 2010 were used. Each colt group and filly group was divided into 2 groups, respectively, and raised in Hidaka or Miyazaki for 7 months from September at 1 year old to April at 2 years old. For the growth parameters, the body weight, height at withers, and girth and cannon circumferences were measured once a month. For parameters of endocrine function, circulating prolactin, luteinizing hormone (LH), follicle-stimulating hormone (FSH), insulin-like growth factor-1 (IGF-1), testosterone, progesterone, and estradiol-17β levels were measured. Regarding growth, the rate of increase over the 7-month period was significantly higher in both colts and fillies raised in Miyazaki than in Hidaka in all 4 parameters: body weight, height at withers, and girth and cannon circumferences. The endocrine changes of the colts and fillies born in 2007 were as follows. In colts, although circulating prolactin tended to be higher in colts reared in Hidaka from October to April, circulating LH, FSH, testosterone, estradiol-17β and IGF-1 tended to be higher in colts reared in Miyazaki than in Hidaka, suggesting that the gonadotropin-releasing hormone-LH/FSH system and the growth hormone-IGF-1 system were more active in colts reared in Miyazaki as compared with those reared in Hidaka. In fillies, circulating prolactin tended to be higher in fillies reared in Hidaka in February and March, but no significant difference was noted in the serum LH, FSH, IGF-1, or progesterone level between the 2 groups. Circulating estradiol-17β tended to be higher in fillies reared in Miyazaki than in Hidaka in October and November. Regarding ovarian function, the initial ovulation occurred by the end of March in 2 (16.7%) of 12 fillies reared in Hidaka and 7 (38.9%) of 18 fillies reared in Miyazaki, suggesting that the ovarian function was more active in fillies reared in Miyazaki as compared with those reared in Hidaka. Based on these findings, it was clarified that development of the body and gonads was faster in Miyazaki compared with Hidaka in both colts and fillies.

Predominant role of the hypothalamic-pituitary axis, not the ovary, in different types of abnormal cycle induction by postnatal exposure to high dose p-tert-octylphenol in rats

To determine whether it is the hypothalamic-pituitary axis or the ovary that plays the predominant role in abnormal estrous cycling induction by postnatal exposure to estrogenic compounds, female rats were subcutaneously injected with 100mg/kg p-tert-octylphenol or vehicle for 5 or 15 days after birth (OP-PND5, OP-PND15 or control). Ovaries were exchanged between control and treated groups on PND28. Controls receiving control or OP-PND5 ovaries showed normal cycles within 4 weeks after the exchange, and corpora lutea were detected in transplanted ovaries. Controls receiving OP-PND15 ovaries consistently increased persistent estrus (PE). OP-PND15 rats receiving control or OP-PND15 ovaries immediately descended into PE, and transplanted ovaries were atrophic with cystic follicles, indicating anovulation. OP-PND5 rats receiving control or OP-PND5 ovaries showed early onset of PE after normal cycling. The hypothalamic-pituitary axis is predominant in abnormal cycling induction by postnatal exposure to OP. OP-PND15 ovaries were impaired compared to other groups.

Early indicators of delayed adverse effects in female reproductive organs in rats receiving neonatal exposure to 17alpha-ethynylestradiol

We previously reported that neonatal exposure to 17α-ethynylestradiol (EE) led to delayed adverse effects in which age-related anovulation after sexual maturation was accelerated. To identify early indicators of these adverse effects, female Wistar Hannover GALAS rats received a single EE injection (0, 0.02, 0.2, 2, 20, or 200 μg/kg) within 24 hr of birth. Histopathological changes in ovarian and uterine development were investigated from postnatal day (PND) 14 to 10 weeks of age. Immunohistochemical expression of estrogen receptor alpha (ERα) in the uterus, serum levels of sex-related hormones and gene expression in the hypothalamus were examined. Although neonatal exposure to EE did not affect body growth or ovarian development, serum FSH tended to decrease at doses ≥ 2 μg/kg, and Kiss1 mRNA level in the whole hypothalamus was significantly decreased in all EE-treated groups at PND14.The number of uterine glands at PND21 was suppressed at doses ≥ 20 μg/kg, and ERα expression in the uterine epithelium at estrus stage decreased in a dose-dependent manner at 10 weeks of age. These results demonstrated that the various identified changes that occurred before the appearance of delayed adverse effects could be candidate early indicators.

Declining semen quality and steadying seminal plasma ions in heat-stressed boar model

Purpose

There are increasing concerns about infertility of male exposure to high environmental temperatures. Nevertheless, the relationship between heat and accessory sex gland secretion underlying the high ambient temperature-induced poor semen quality has not yet been addressed.

Methods

In the present study, five boars were used as an animal model to evaluate semen quality and the secretory function of accessory sex glands. After the boars received 3 days of heat exposure, semen collection was standardized to 18 continual times with a 3-day interval to determine the semen variables of semen volume, semen concentration, abnormal spermatozoa, seminal plasma composition, and testosterone level in the seminal plasma and serum.

Results

The total sperm count was lowest by the end of week 2. The higher abnormal spermatozoa percentage were observed by the end of week 2 and persisted until week 6 after heat exposure. Additionally, there was no significant change in semen volume, testosterone level, and concentrations of ions and total protein in the seminal plasma before and after heat exposure.

Conclusions

A single 3-day heat exposure caused poor semen quality, but did not disturb accessory sex gland secretion in boars. Declining semen quality might be mainly due to the damaged germ cells, which were sensitive to elevated temperature in hot summer months.

Effect of a single injection of gonadotropin-releasing hormone (GnRH) and human chorionic gonadotropin (hCG) on testicular blood flow measured by color doppler ultrasonography in male Shiba goats

Although color Doppler ultrasonography has been used to evaluate testicular blood flow in many species, very little has been done in goat. Eight male Shiba goats were exposed to a single intramuscular injection of either gonadotropin-releasing hormone (GnRH group; 1 µg/kg BW) or human chorionic gonadotropin (hCG group; 25 IU/kg BW). Plasma testosterone (T), estradiol (E2) and inhibin (INH) were measured just before (0 hr) and at different intervals post injection by radioimmunoassay. Testis volume (TV) and Doppler indices, such as resistive index (RI) and pulsatility index (PI) of the supratesticular artery, were measured by B-mode and color Doppler ultrasonography, respectively. The results indicated an increase in testicular blood flow in both groups, as RI and PI decreased significantly (P<0.05), but this increase was significant higher and earlier in hCG group (1 hr) than in the GnRH group (2 hr). A high correlation was found for RI and PI with both T (RI, r= −0.862; PI, r= −0.707) and INH in the GnRH group (RI, r=0.661; PI, r=0.701). However, a significant (P<0.05) correlation was found between E2 and both RI (r= −0.610) and PI (r= −0.763) in hCG group. In addition, TV significantly increased and was highly correlated with RI in both groups (GnRH, r= −0.718; hCG, r= −0.779). In conclusion, hCG and GnRH may improve testicular blood flow and TV in Shiba goats.

4-Nitro-3-phenylphenol has both androgenic and anti-androgenic-like effects in rats

To investigate the effect of endocrine disruption of 4-nitro-3-phenylphenol (PNMPP) on immature male Wistar-Imamichi rats, the rat pituitary was exposed to PNMPP (10^–5–10^–9 M) for 24 h with or without gonadotropin-releasing hormone (GnRH) in experiment I. In addition, the Leydig cells (10^–5–10^–9 M) were exposed to PNMPP for 24 h with or without human chronic gonadotropin (hCG) in experiment II. Our results showed that the PNMPP at 10^–5–10^–7 M suppressed follicle-stimulating hormone (FSH) and luteinizing hormone (LH) productions from GnRH-stimulated pituitary cells. At the same time, PNMPP 10^–5–10^–7 M induced an increase in testosterone production from the Leydig cells treated with or without hCG. Based on our results, it can be concluded that that PNMPP might have both androgen agonist action by decreasing FSH and LH production in the pituitary and anti-androgenic action by increasing testosterone production in the Leydig cell.

Expression of P450arom and Estrogen Receptor Alpha in the Oviduct of Chinese Brown Frog (Rana dybowskii) during Prehibernation

One specific physiological phenomenon of Chinese brown frog (Rana dybowskii) is that its oviduct expands prior to hibernation instead of expanding during the breeding period. In this study, we investigated the expression of P450arom and estrogen receptors α and β (ERα and ERβ) in the oviduct of Rana dybowskii during the breeding period and prehibernation. The results of the present study showed that there were significant differences in both oviductal weight and size with values markedly higher in prehibernation than in the breeding period. P450arom was observed in stromal tissue in both the breeding period and prehibernation. ERα was expressed in stromal tissue and epithelial cells in both periods, whereas ERβ could not be detected. The mean protein and mRNA levels of P450arom and ERα were significantly higher in prehibernation as compared to the breeding period. Besides, oviductal content of 17β-estradiol was also higher in prehibernation than in the breeding period. These results suggested that estrogen may play autocrine/paracrine roles mediated by ERα in regulating the oviductal hypertrophy during prehibernation.

Low-dose gold nanoparticles exert subtle endocrine-modulating effects on the ovarian steroidogenic pathway ex vivo independent of oxidative stress

Gold nanoparticles (GNPs) have gained considerable attention for application in science and industry. However, the untoward effects of such particles on female fertility remain unclear. The objectives of this study were to (1) examine the effects of 10-nm GNPs on progesterone and estradiol-17β accumulation by rat ovaries ex vivo and (2) to identify the locus/loci whereby GNPs modulate steroidogenesis via multiple-reference gene quantitative real-time RT-PCR. Regression analyses indicated a positive relationship between both Star (p < 0.05, r(2) = 0.278) and Cyp11a1 (p < 0.001, r(2) = 0.366) expression and P4 accumulation upon exposure to 1.43 × 10(6) GNPs/mL. Additional analyses showed that E2 accumulation was positively associated with Hsd3b1 (p < 0.05, r(2) = 0.181) and Cyp17a1 (p < 0.01, r(2) = 0.301) expression upon exposure to 1.43 × 1(3) and 1.43 × 10(9) GNPs/mL, respectively. These results suggest a subtle treatment-dependent impact of low-dose GNPs on the relationship between progesterone or estradiol-17β and specific steroidogenic target genes, independent of oxidative stress or inhibin.

GnRH analogue treatment on LH surge day 0 followed by single transvaginal artificial insemination with frozen semen on day 5 in bitches

Reproductive parameters were evaluated in 19 and 14 estrous beagles that received 100 µg of gonadotropin-releasing hormone (GnRH) and saline treatment, respectively, on the day of luteinizing hormone (LH) surge (Day 0; estimated by serial progesterone assay) and balloon catheter-aided single transvaginal artificial insemination of frozen semen on Day 5. Although the conception rate and litter size were similar between the GnRH and saline groups, the concentration of LH peak was significantly higher in GnRH-treated bitches (P<0.01). In addition, the actual LH surge did not occur on the estimated Day 0 in one saline-treated bitch. In clinical practice that daily progesterone assay is difficult, administration of GnRH on estimated Day 0 would be recommended to induce or enhance the LH surge for timely and successful insemination.

Seasonal expression of androgen receptor in scented gland of muskrat (Ondatra zibethicus)

Muskrat is a seasonal breeder, males of which secret musk from paired perineal scented glands found beneath the skin at the ventral base of the tail for attracting female during the breeding season. The aim of this study was to investigate the seasonal changes of expression of androgen receptor (AR) in the scented gland of muskrat during the breeding and nonbreeding seasons. Histologically, glandular cells, interstitial cells and excretory tubules were identified in scented glands in both seasons, whereas epithelial cells were sparse in the nonbreeding season. AR was observed in glandular cells of scented glands during the breeding and nonbreeding seasons with stronger immunostaining during the breeding season compared to the nonbreeding season. Consistent with the immunohistochemical results, AR protein level was higher in the scented glands of the breeding season, and then decreased to a relatively low level in the nonbreeding season. The mean mRNA level of Ar was significantly higher in the breeding season than in the nonbreeding season. In addition, plasma gonadotropins and testosterone concentrations were remarkably higher in the breeding season than those in the nonbreeding season. These results suggested that muskrat scented gland was the direct target organ of androgen, and stronger expression of AR in scented glands during the breeding season suggested that androgens may directly influence scented glandular function of the muskrats and also courtship behavior as we inferred.

Low expression of the antibacterial factor L-amino acid oxidase in bovine mammary gland

In the mouse, L-amino acid oxidase (LAO) produces hydrogen peroxide by utilizing free amino acids and is a proven antibacterial factor in mammary glands. Mastitis, a bacterial infection of the mammary gland, is the most frequent disease in dairy cattle. Here, we investigate whether LAO is expressed in the mammary gland of dairy cattle and is antibacterial. In dairy cattle, the expression level of LAO mRNA in the mammary gland was considerably lower than that in mice, and LAO activity was not observed in cattle milk that produced hydrogen peroxide. The expression of LAO mRNA was also low in Japanese Black cattle, the same as in Holstein cattle. A higher LAO mRNA expression was observed in the mastitis glands than in the lactating glands. Furthermore, spleen and lymph nodes expressed high levels of LAO mRNA in dairy cattle. We conclude that mammary glands in dairy cattle have lower ability to express the LAO gene compared to that in mice, which may result in a high incidence of mastitis.

Effect of Postbreeding Intramuscular Administration of Deslorelin Acetate on Plasma LH and Progesterone Concentrations and Conception Rate in Mares

To clarify effect of postbreeding intramuscular administration of deslorelin on mares, plasma LH and progesterone concentrations and conception rate were evaluated. In Experiment 1, deslorelin, buserelin, or a placebo was administered on day 9 (day 0=day of last breeding or AI). Plasma samples were collected daily from days 6 to 15, and additional samples were taken after treatment. There was a significant increase in hormonal concentrations after deslorelin treatment. In Experiment 2, deslorelin or placebo was injected on day 9. There was no difference in conception rates at days 15 and 30 between the two groups. While a single postbreeding treatment of deslorelin increased peripheral LH and progesterone concentrations, it may not affect the conception rate in mares.

Neonatal exposure to 17α-ethinyl estradiol affects kisspeptin expression and LH-surge level in female rats

Contamination of estrogenic compounds disrupts endocrinological and neurological reproductive systems in animals. Neonatal exposure to 17α-ethinyl estradiol (EE) induced an abnormal estrous cycle at postnatal day (PND) 180, but not at PND90. We found that serum level of luteinizing hormone (LH) at the latter half of proestrus in EE-treated rats was lower than in the controls at PND90 when there was no significant difference on estrous cyclicity. Additionally, kiss1 mRNA levels in the anteroventral periventricular nucleus-preoptic area (AVPV/POA) were lower in EE-treated rats than in the controls. The expression of GnRH precursor (GNRH1) mRNA in the AVPV/POA and that of LH beta subunit (LHb) mRNA in the pituitary were similar in the control- and EE-treated groups. Our results indicated that neonatal exposure to EE leads to reduced expression of kiss1 mRNA in AVPV/POA and LH-surge, which is likely related to the delayed reproductive dysfunction seen in adult female rats.

Neonatal exposure to 17α-ethynyl estradiol affects ovarian gene expression and disrupts reproductive cycles in female rats

Neonatal exposure to synthetic estrogen causes delayed reproductive dysfunction in female rats. Exposure to 17α-ethynyl estradiol (EE, low: 20 and high: 2000 μg/kg) induced an abnormal estrous cycle during PND171-190 in low-dose and PND126-145 in high-dose group. At PND90 within normal estrous cycle, high-dose animals showed lack of LH surge and low of ovarian hormones in serum level. Gene expression analysis demonstrated that level of mRNA encoding luteinizing hormone/chorionic gonadotropin receptor (LHCGR) was higher in EE-treated ovaries than in control ovaries, and LHCGR protein colocalized with apoptosis-related proteins in the interstitial area of the ovary. At PND1, ovarian LHCGR mRNA levels were higher in EE-treated rats than in control rats, and direct induction of LHCGR expression by EE was observed in vitro. Our results indicate that neonatal exposure to EE induces irregular LHCGR expression in the immature ovary, which may influence the occurrence of delayed reproductive dysfunction in adult animals.

Preventive effect of tert-butylhydroquinone on scrotal heat-induced damage in mouse testes

To investigate the effect of tert-butylhydroquinone (tBHQ) on scrotal heat-induced damage in mice testes, 8-week-old mice were divided into 6 groups and administered with or without tBHQ through diet (10 mg/g), intraperitoneal injection (100 mg/kg body weight), or intratestis injection (12.5 mg/kg body weight), respectively. After single scrotal heat exposure (42 °C for 25 min), trunk blood and testes were collected 48 h later. The testes from diet and intraperitoneal tBHQ-treated mice showed more compact interstitial cells and less germ cell loss in the seminiferous epithelium compared with their corresponding non-tBHQ groups. However, intratestis tBHQ treatment showed no marked difference relative to the non-treatment group. In addition, pre-treatment of tBHQ caused lower testosterone concentrations and reduced expression of cytochrome P450 17α-hydroxylase/17,20-lyase (CYP 17) compared to the corresponding non-tBHQ groups. The results indicated that scrotal heat-induced structural damage was partly prevented by pre-treatment of tBHQ, which could be used as an effective antioxidant for preventing scrotal heat-mediated male infertility.

Reduced responsiveness of kisspeptin neurons to estrogenic positive feedback associated with age-related disappearance of LH surge in middle-age female rats

Age-related disappearance of the LH surge is one of major biomarkers of reproductive aging in female rats. Kisspeptin neurons in the hypothalamic anteroventral periventricular nucleus (AVPV) are proposed as the critical regulator of the preovulatory LH surge in response to estrogenic positive feedback. Here we investigated the possible involvement of the AVPV kisspeptin neurons in the disappearance of the LH surge in middle-age rats. Middle-age rats exhibiting persistent estrus (M-PE) did not show an LH surge although neither Kiss1 mRNA nor peptide in the AVPV was differentially expressed when compared to young rats exhibiting normal estrous cycles (YN). M-PE released LH in response to exogenous kisspeptin in a similar dose-dependent manner as YN, suggesting that their GnRH neurons still maintained responsiveness to kisspeptin. To investigate the estrogenic positive feedback effect on kisspeptin neurons in the AVPV, rats were ovariectomized and supplemented with estradiol (OVX+E2). We performed in situ hybridization and immunohistochemistry for Kiss1 mRNA and cFos, respectively, and found that M-PE exhibited a significantly lower percentage of Kiss1 mRNA positive neurons with cFos immunoreactivity, although the total number of kisspeptin neurons was not different from that in cyclic rats. Furthermore, OVX+E2 M-PE did not show the surge-like LH release under high estradiol administration while YN did. Thus our current study suggests that the reduced responsiveness of the AVPV kisspeptin neurons to estrogenic positive feedback presumably results in the decrease in kisspeptin secretion from neurons and eventually causes the age-related disappearance of the LH surge in middle age female rats.

Delayed effects of neonatal exposure to 17alpha-ethynylestradiol on the estrous cycle and uterine carcinogenesis in Wistar Hannover GALAS rats

We investigated the delayed effects of neonatal exposure to 17α-ethynylestradiol (EE) on the female reproductive tract using Wistar Hannover GALAS rats. Female pups received single injections of EE (0, 0.02, 0.2, 2, 20, or 200 μg/kg) within 24h after birth and estrous cyclicity was observed until 10 months of age. All animals were treated at 9 weeks of age with the uterine carcinogen, N-ethyl-N'-nitro-N-nitrosoguanidine. Although the vaginal opening was not affected, abnormal cycles were significantly increased from 0.2 μg/kg. Persistent estrus was prominent and the incidence increased age- and dose-dependently. Severity of atypical hyperplasia of the uterus tended to increase from 2 μg/kg. In these groups, serum progesterone level was lowered relative to estradiol level. In conclusion, estrous cyclicity was a sensitive indicator reflecting delayed effects on the female reproductive tract. Early onset of anovulation leading to prolonged estrogen exposure might be a risk factor for uterine carcinogenesis.

Male Hatano high-avoidance rats show high avoidance and high anxiety-like behaviors as compared with male low-avoidance rats

Our prime objective was to establish an optimal model animal for studying avoidance learning and memory in rodents. The two-way rat inbred strains of Hatano high- (HAA) and low-avoidance (LAA) animals were originally selected and bred in accordance with their high or low performance respectively in the shuttle-box active avoidance task. Previous studies demonstrated that they have clear strain differences in endocrine stress response, which is related to acquisition of aversive learning and emotional reactivity. To evaluate the effect of selection by the shuttle-box task on avoidance performance and emotional reactivity, male Hatano rats underwent passive avoidance, open field and elevated plus maze tests. The present results show that the avoidance performance in the passive task was significantly greater in HAA rats than in LAA rats. Furthermore, HAA rats showed high anxiety-like behaviors compared with LAA rats in open field and elevated plus maze tests. Taken together, this study demonstrated that 1) selection and breeding of Hatano HAA and LAA strain rats by shuttle-box task had been properly carried out with the criterion of high and low avoidance performance respectively and that 2) HAA rats were predisposed to high anxiety compared with LAA rats. These results indicated that Hatano HAA and LAA rats can be useful models for studying avoidance learning and memory.

Pregnancy-associated plasma protein (PAPP)-A expressed in the mammary gland controls epithelial cell proliferation and differentiation

Lactation is an important event in all-mammalian species. To investigate the role of pregnancy-associated plasma protein (PAPP)-A in lactogenesis, we determined (i) PAPP-A expression in mouse mammary glands and (ii) the biological functions of PAPP-A in mammary epithelial cells. PAPP-A mRNA level was low during early mid pregnancy and increased during mid-late pregnancy, and then slightly decreased during lactation. Cell proliferation signals, but not differentiation, increased PAPP-A mRNA expression in HC11 mammary epithelial cells. Treatment of recombinant PAPP-A protein stimulated HC11 cell proliferation and suppressed the expression of β-casein mRNA, which is one of the milk proteins and cell differentiation marker. Surprisingly, in forcing expression experiment, PAPP-A increased β-casein mRNA expression. Our data suggest that PAPP-A has different roles on intracellular expressing and extracellular treatment to mammary epithelial cells. Taken together, in early pregnancy, circulating PAPP-A protein might be supplied from other organs and stimulates mammary gland growth. In contrast, during mid-late pregnancy, local PAPP-A expression begins and enhances cell differentiation within mammary epithelial cell.

Seasonal changes in immunoreactivity of inhibin/activin subunits in the epididymis of wild ground squirrels (Citellus dauricus Brandt)

The inhibin/activin subunits (α, βA and βB) have been found in epididymal tissue of many mammals, but there have been no data available for wild seasonal breeders so far. The aim of this study was to investigate the immunoreactivities of inhibin/activin α, βA and βB subunits in the epididymis of wild ground squirrels during the breeding and nonbreeding seasons. Immunohistochemistry and Western blotting were performed to detect the epididymal immunolocalizations and immunoreactivities of the three subunits. Strong immunostaining of α subunit was present in the interstitial part of the caput epididymis and epithelial parts of the corpus epididymis and cauda epididymis during the breeding season, whereas no α subunit was found in the nonbreeding season. βA and βB subunits were expressed in all cell types of the epithelium throughout the whole seasonal cycle, and immunostaining in the breeding season was likely stronger compared with that of the nonbreeding season. These results suggested that the epididymis might be a potential source of inhibin and activin in the wild male ground squirrel, and the secretion of epididymal inhibin and activin showed distinct seasonal changes. Furthermore, inhibin and activin might function as paracrine and/or autocrine factors that have an effect on the epididymis.

Protective effects of nuclear factor erythroid 2-related factor 2 on whole body heat stress-induced oxidative damage in the mouse testis

BACKGROUND

Whole body heat stress had detrimental effect on male reproductive function. It's known that the nuclear factor erythroid 2-related factor 2 (Nrf2) activates expression of cytoprotective genes to enable cell adaptation to protect against oxidative stress. However, it's still unclear about the exactly effects of Nrf2 on the testis. Here, we investigate the protective effect of Nrf2 on whole body heat stress-induced oxidative damage in mouse testis.

METHODS

Male mice were exposed to the elevated ambient temperature (42°C) daily for 2 h. During the period of twelve consecutive days, mice were sacrificed on days 1, 2, 4, 8 and 12 immediately following heat exposure. Testes weight, enzymatic antioxidant activities and concentrations of malondialdehyde (MDA) and glutathione (GSH) in the testes were determined and immunohistochemical detection of Nrf2 protein and mRNA expression of Nrf2-regulated genes were analyzed to assess the status of Nrf2-antioxidant system.

RESULTS

Heat-exposed mice presented significant increases in rectal, scrotal surface and body surface temperature. The concentrations of cortisol and testosterone in serum fluctuated with the number of exposed days. There were significant decrease in testes weight and relative testes weight on day 12 compared with those on other days, but significant increases in catalase (CAT) activity on day 1 and GSH level on day 4 compared with control group. The activities of total superoxide dismutase (T-SOD) and copper-zinc SOD (CuZn-SOD) increased significantly on days 8 and 12. Moreover, prominent nuclear accumulation of Nrf2 protein was observed in Leydig cells on day 2, accompanying with up-regulated mRNA levels of Nrf2-regulated genes such as Nrf2, heme oxygenase 1 (HO-1), γ-Glutamylcysteine synthetase (GCLC) and NAD (P) H: quinone oxidoreductase 1 (NQO1)) in heat-treated groups.

CONCLUSIONS

These results suggest that Nrf2 displayed nuclear accumulation and protective activity in the process of heat treated-induced oxidative stress in mouse testes, indicating that Nrf2 might be a potential target for new drugs designed to protect germ cell and Leydig cell from oxidative stress.