Steroidogenic potential of the gonad during sex differentiation in the rice field frog Hoplobatrachus rugulosus (Anura: Dicroglossidae).

Prior studies demonstrated that gonadal differentiation in the rice field frog, Hoplobatrachus rugulosus, was of an undifferentiated type since all individuals had ovaries at complete metamorphosis. However, the steroidogenic potential of the gonad is still unknown. In this study, H. rugulosus were obtained by stimulating fertilization in the laboratory under natural light and temperature conditions. The gonads were collected and their steroidogenic potential was evaluated by determining the expression level of messenger RNA (mRNA) encoding for cytochrome P450 17-hydroxylase/C17-20 lyase (CYP17) and cytochrome P450 aromatase (CYP19) using quantitative real-time RT-PCR and the localization of CYP17 mRNA in tissues by in situ hybridization. The CYP17 mRNA levels in males at 4-11 weeks postmetamorphosis were higher than in female and intersex gonads. This corresponded to their localization in the gonadal tissues, where CYP17 signals were specifically detected in the Leydig cells of the testis at 5-16 weeks postmetamorphosis but was undetectable in all ovary samples. The CYP19 mRNA levels in females at 4-11 weeks postmetamorphosis was higher than in male and intersex gonads, which corresponded with gonadal development, indicating the potential steroidogenic function of the ovary. Based on the present results, the role of CYP17 and CYP19 mRNA in sex differentiation in H. rugulosus may occur after gonadal sex differentiation and the steroidogenic potential of the gonads exhibited a sexual dimorphic pattern. These results provide a crucial basis for further research on the developmental biology in anuran species.

Comparison of neuroprotective effects of dihydrotestosterone, 17ß-estradiol, and Pueraria mirifica herb extract on cognitive impairment in androgen deficient male rats.

This study investigated the neuroprotective effects of dihydrotestosterone (DHT), 17ß-estradiol (E2), and Pueraria mirifica herb extract (PME; an alternative source of natural estrogens) on the (i) learning and memory in androgen-deficient male rats, and on the hippocampus expression levels of (ii) mRNA of genes associated with synaptic transmission and structure, neurofibrillary tangles, and amyloid plaques, and (iii) total and phosphorylated tau proteins. The four-month-old male rats were sham-operated or orchidectomized (ODX). The ODX rats were divided into four groups, and orally treated for 2 months with either 1 mL/d of distilled water or 100 mg/kg/d of PME; or subcutaneously injected with 1 mg/kg/d of DHT or 80 µg/kg/d of E2. The impairment of spatial learning behavior and memory capacity in the ODX rats was prevented by DHT, E2, and PME. Recovery of the orchidectomy-induced deterioration of the synaptic plasticity in the hippocampus of rats was ranked as E2 ≥ PME > DHT. Both DHT and PME mitigated the increased Tau3 and Tau4 mRNA levels, and Tau-5 and P-Tau Ser396 protein levels more than E2 (DHT ≥ PME > E2). Only DHT tended to decrease App mRNA expression level. In conclusion, DHT showed a stronger efficacy for mitigation of the impaired spatial learning behavior and memory capacity in androgen-deficient male rats compared to E2 and PME, and their mechanisms of action are slightly different.

Chronological Molecular Changes in Neuronal Communication in Androgen-Deficient Rats.

We investigated the early onset of molecular changes in the hippocampus of orchidectomy (ODX)-induced androgen-deficient rats. Transcript levels of the genes associated with loss of synaptic plasticity (Bdnf, Syn, GluN1, α7-nAChR, and M1-mAChR), formation of neurofibrillary tangles (Tau4 and Tau3), and amyloid plaques (App, Adam10, and Bace1), in the hippocampus of rats at 0, 1, 3, 6, and 9 days after ODX (D0, D1, D3, D6 and D9, respectively) were determined. Primarily, the sudden loss of androgen, as confirmed by the decreased serum testosterone levels and accessory sex organ weights, induced a chronological reduction in Syn (at D1), and increase in GluN1 (at D3), α7-nAChR, and M1-mAChR (at D6) and a decrease in Bdnf (at D9) transcript levels. Tau4 and Tau3 mRNA levels were increased at D6 and D9, respectively. No changes in App, Adam10, and Bace1 mRNA levels were detected within the 9-day study period. To confirm those changes were caused by androgen deprivation and not increasing age, the mRNA expression levels of those genes in 9-day orchidectomized rats (ODX-D9) were compared with age-matched intact rats. All changes of mRNA expression levels of the ODX-D9 rats were aligned with the D9 rats, except for GluN1 that was decreased in the ODX-D9 rats. Moreover, the total and phosphorylated tau protein levels were increased in the ODX-D9 rats. These results denote that androgen deficiency induces the early onset of neurodegeneration, while the loss of synaptic plasticity together with the formation of neurofibrillary tangles could be used as markers for neurodegenerative prediction.

Collagen and mPCL-TCP scaffolds induced differential bone regeneration in ovary-intact and ovariectomized rats.

BACKGROUND: The data on biomaterial-mediated bone regeneration directly comparing commercially available scaffolds in aging and osteoporotic conditions remain sparse. OBJECTIVE: To investigate the effects of an absorbable collagen sponge (ACS) and a medical grade polycaprolactone-tricalcium phosphate (mPCL-TCP) scaffold on calvarial defect healing in ovary-intact and ovariectomized rats. METHODS: Forty-two, 5-month old female Sprague-Dawley rats were divided into sham (OVI) or ovariectomy (OVX) groups (n=21). When rats reached 6 months old, 7 mm diameter calvarial defects were created and treated, further dividing each group into blood clot control, mPCL-TCP, or ACS subgroups (n=7). After four weeks, the calvarial specimens were evaluated using micro-computed tomography for bone volume fraction (BVF), and histopathology. RESULTS: The effects of ovariectomy were confirmed by changes in body, uterine, and vaginal weight, and osteopenia in the femur. A significant increase in BVF was observed in ACS-subgroups compared with their respective control groups (p<0.05). Histopathological analysis revealed no cellular inflammatory infiltrate in any group. Fibrous tissue encapsulated the mPCL-TCP, while the ACS was well-integrated with the bone matrix. The OVX groups presented more osteoid and enlarged marrow cavities compared with the OVI groups. CONCLUSION: ACS scaffold enhanced calvarial bone regeneration in OVI and OVX rats after four weeks.

Acemannan increased bone surface, bone volume, and bone density in a calvarial defect model in skeletally-mature rats.

BACKGROUND/PURPOSE: Acemannan, a ß-(1-4)-acetylated polymannose extracted from Aloe vera gel, has been proposed as biomaterial for bone regeneration. The aim of this study was to investigate the effect of acemannan in calvarial defect healing. MATERIALS AND METHODS: Acemannan was processed to freeze-dried sponge form and disinfected by UV irradiation. Thirty-five female Sprague-Dawley rats were used in the in vivo study. Seven-mm diameter mid-calvarial defects were created and randomly allocated into blood clot control (C), acemannan 1 mg (A1), 2 mg (A2), 4 mg (A4), and 8 mg (A8) groups (n = 7). After four weeks, the calvarial specimens were subjected to microcomputed tomography (microCT) and histopathological analysis. RESULTS: MicroCT revealed a significant increase in bone surface and bone volume in the A1 and A2 groups, and tissue mineral density in the A4 and A8 groups compared with the control group (p < 0.05). Histologically, the acemannan-treated groups had denser bone matrix compared with the control group. CONCLUSION: Acemannan is an effective bioactive agent for bone regeneration, enhancing bone growth as assayed in two- and three-dimensions.

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.

Neurotherapeutic Effects of Pueraria mirifica Extract in Early- and Late-Stage Cognitive Impaired Rats.

We determined the neurotherapeutic effects of Pueraria mirifica extract (PME) and pure puerarin (PU) in comparison with 17ß-estradiol (E2 ) in early- and late-stage cognitive impaired rats. Rats were ovariectomized (OVX), kept for 2 and 4 months to induce early- and late-stage cognitive impairment, respectively, and divided into four groups that were treated daily with (i) distilled water, (ii) 100 mg/kg of PME, (iii) 7 mg/kg of PU, and (iv) 80 µg/kg of E2 for 4 months. The estrogen deficiency symptoms of OVX rats were abrogated by treatment with E2 or PME, but not by treatment with PU. The mRNA level of genes associated with amyloid production (App and Bace1) and hyperphosphorylated Tau (Tau4) were upregulated together with the level of impaired cognition in the 2- and 4-month OVX rats. Treatment with E2 reduced the level of cognitive impairment more than that with PME and PU, and 2-month OVX rats were more responsive than 4-month OVX rats. All treatments down-regulated the Bace1 mRNA level in 2-month OVX rats, while PU and PME also decreased the App mRNA level in 2- and 4-month OVX rats, respectively. Only PU suppressed Tau4 expression in 2-month OVX rats. Thus, PME and PU elicit neurotherapeutic effects in different pathways, and earlier treatment is optimal. Copyright © 2016 John Wiley & Sons, Ltd.

Anti-osteoporotic effects of Pueraria candollei var. mirifica on bone mineral density and histomorphometry in estrogen-deficient rats.

Although it has been clearly shown that Pueraria mirifica and its phytoestrogens can mimic estrogen in preventing bone loss, as osteoporosis is an asymptomatic disease, the therapeutic effects of P. mirifica should be acknowledged. In this study, 6-month-old female rats were ovariectomized, kept for 4 weeks to induce bone loss, divided into five groups, and treated with P. mirifica at doses of 0, 5, 25, and 50 mg/kg BW/day (PM0, PM5, PM25, and PM50 groups, respectively) or 7 mg/kg BW/day of puerarin (PU group) for 12 weeks. Only the trabecular bone mineral densities (BMDs) of tibia metaphysis (at the 12th, 14th, and 16th week) and total and trabecular BMDs of L4 (at the 16th week) of the PM50 group were significantly higher than those of the PM0 group. However, the BMDs of tibia metaphysis and L4 at the 16th week of the study period were kept significantly lower than those of the 0 week, and the BMD was also significantly lower than that of the 4th week for tibia metaphysis. The trabecular bone area (BV/TV), trabecular number (Tb.N), and osteoblast surface (Ob.S/BS) were significantly higher, and trabecular space (Tb.Sp) was significantly lower in the PM50 group, as compared with those of the PM0 group. This study indicates that P. mirifica could be used as an anti-osteoporotic agent for postmenopausal women. Since P. mirifica could mainly retain bone mass at the levels before bone loss is initiated, the use of other anabolic agents in combination with P. mirifica is recommended for osteoporotic patients.

Improvements of vaginal atrophy without systemic side effects after topical application of Pueraria mirifica, a phytoestrogen-rich herb, in postmenopausal cynomolgus macaques.

The estrogenic efficacy of topical vaginal application of Pueraria mirifica extract (PM) on the restoration of vaginal atrophy, and the presence of any systemic side effects, were investigated in postmenopausal cynomolgus macaques. Twelve postmenopausal cynomolgus macaques, with complete cessation of menstruation for at least 5 years before start of this experiment, were divided into three groups. They received a topical vaginal application daily of 0.1 or 1% (w/w) PM cream or a conjugated equine estrogen (CEE) cream (a mixture of estrone, equilin, 17ß-dihydroequilin, 17α-estradiol and 17α-dihydroequilin at 0.625 mg total estrogen/g cream) for 28 days. Estrogenic efficacy was assessed weekly by vaginal cytology assay and vaginal pH measurement, whilst the plasma luteinizing hormone (LH) and sex skin coloration levels were determined at the end of each treatment period to evaluate the systemic side effects. PM significantly increased the proportion of superficial cells in a dose-dependent manner, with a similar efficacy between 1% (w/w) PM and CEE. Together with increased vaginal maturation, PM decreased the vaginal pH to acidic levels, as observed in the CEE group. PM induced no detected systemic side effects, whilst CEE decreased the plasma LH level and increased the reddish color of the sex skin during the posttreatment period. Topical vaginal treatment with PM stimulated the maturation of the vaginal epithelium without causing systemic side effects in postmenopausal monkeys. The implication is that PM could be a safer alternative to treat vaginal atrophy in postmenopausal women.

Molecular events during the induction of neurodegeneration and memory loss in estrogen-deficient rats.

This study aims to delineate the relationship among estrogen deficiency, neurodegeneration, and cognitive impairment of ovariectomized rats. Female Sprague-Dawley rats were ovariectomized and euthanized after 1-4 month periods (M(0)-M(4) groups). Blood samples were collected for the determination of serum levels of 17ß-estradiol (E(2)), luteinizing hormone (LH), and follicle stimulating hormone (FSH). Five consecutive days before the euthanization, cognitive performance of the rats was examined by Morris water maze test. After euthanization, the hippocampus was collected, and expression of the genes associated with amyloid plaques (App, Adam10 and Bace1) and neurofibrillary tangles (Tau4 and Tau3) were examined by real-time PCR. Serum E(2) levels were declined following 2 weeks of ovariectomy. Conversely, serum FSH and LH levels were profoundly increased by 2 weeks of ovariectomy for approximately 4 and 22 times, respectively. Cognitive impairments, indicated by the longer latency and distance, were observed only in the M(3) and M(4) groups. The Tau4 mRNA levels were significantly increased as early as 1 month after ovariectomy (in the M(1) group; P<0.05), and tended to be increased further with the advancing time. Similarly, the Tau3 mRNA levels were increased by ovariectomy, but with the highest level in the M(1) group, and decreased thereafter. The mRNA levels of App, Adam10 and Bace1 were increased by ovariectomy, but significant differences were observed only in the M(4) group. These results indicate that estrogen deficiency can induce a sequence of events that results in the production of neurofibrillary tangles, amyloid deposition, and spatial memory deficit in rats.

Boundary zone between northern and southern pig-tailed macaques and their morphological differences.

Based on previous conflicting reports that the two forms of pig-tailed macaque (northern and southern) exist as separate species, subspecies, or forms, and that their boundary zone lies in Thailand, a survey of the distribution range and morphology of pig-tailed macaques in Thailand was conducted during 2003-2010. We first conducted a questionnaire survey. Questionnaires were sent to 7,410 subdistricts throughout Thailand. We then traveled to 72 of the 123 subdistricts reporting the presence of pig-tailed macaques. However, due to a lack of reports of the presence of free-ranging pig-tailed macaques living south of the Isthmus of Kra, a survey of pet pig-tailed macaques was also conducted during 16-24 September 2011. Furthermore, 35 wild northern pig-tailed macaques inhabiting northern Thailand (13°13'N, 101°03'E) were temporarily caught and their morphological characters were measured and then compared to those of the southern form captured from Sumatra, Indonesia. Although largely allopatric, the ranges of the northern and southern pig-tailed macaques in Thailand were found to have a partially sympatric boundary at the Surat Thani-Krabi depression (8-9°30'N). Morphologically, these two forms were very distinctive, with different morphological characters such as the crown patch, the white color of the triangle above the eyes, the red streak at the external rim of the eyes, pelage color, ischial callosity, tail length and carriage, facial height, and limb length in both sexes, and patterns of sex skin swelling and reddening in females. These differences in morphological characters between the northern and southern forms should help settle the problems of their taxonomy.

Testing of the estrogenic activity and toxicity of Stephania venosa herb in ovariectomized rats.

Stephania venosa Spreng is a traditional herb which has been used for cancer treatment as well as an aphrodisiac. The scientific literature strongly supports its in vitro antiproliferative effects on cancer cell lines and has suggested developing this plant as a potential anticancer drug. However, the in vivo steroidogenic activity and toxicity of this plant have never been tested. We analyzed the levels of five key isoflavones in the plant extract by quantitative HPLC and then evaluated the in vivo estrogenic activity and toxicity in ovariectomized rats, in comparison with the phytoestrogen-rich plant, Pueraria mirifica. Twenty rats were first ovariectomized, and then seven days later divided into four groups and gavaged daily with 0, 10 and 100 mg/kg body weight/day of S. venosa, or 100 mg/kg body weight/day of P. mirifica for 28 days. A trace amount of puerarin, daidzin and daidzein with a subtle amount of genistein and genistin were isolated from the S. venosa tuber extract. S. venosa tuber powder, at both doses, did not exhibit any detectable estrogenic activity in ovariectomized rats, as assessed by the vaginal cytology and uterotropic assays, whilst P. mirifica induced a remarkable vaginal and uterine proliferation. S. venosa induced a toxicological effect on the hematological values and histopathological appearance of metabolic organs. Taken together, these results suggest that S. venosa has no discernable estrogenic activity but that it is toxic, at least to ovariectomized rats. Thus, the use of this plant for anticancer treatment needs to be reassessed or used with caution.

Effects of pantothenic acid supplement on secretion of steroids by the adrenal cortex in female rats.

PURPOSE: The effect of pantothenic acid (PaA) supplementation on adrenal secretion of corticosterone and progesterone in female rats was investigated. METHODS: An in-vitro primary adrenal cell culture system was used. Pregnant rats were given 0.03% PaA in their drinking water throughout pregnancy and the period of lactation. In the first experiment, after weaning, female rats continued to receive 0.03% PaA treatment until 10 weeks of age. The animals were then decapitated and adrenal cells were cultured in the absence or presence of rat adrenocorticotropic hormone (ACTH) for 4 h. In the second experiment, adrenal cells from lactating rats on day 5 of lactation were cultured in the absence or presence of rat ACTH for 4 h. RESULTS: The effect of ACTH at 10-10 m on corticosterone and progesterone release was greater for PaA-treated cyclic rats than for control cyclic rats. The effect of ACTH at 10-10 m on corticosterone release was greater for PaA-treated lactating rats than for control lactating rats. Circulating ACTH and corticosterone levels in PaA-treated and control cyclic and lactating rats were no different. CONCLUSIONS: These results indicate that PaA supplementation induced hyperresponsiveness to ACTH stimulation in cyclic and lactating female rats. These results clearly demonstrated that PaA is an essential factor in adrenal steroidogenesis of female rats.

Endocrinological differences between Hatano high- and low-avoidance rats during early two-way avoidance acquisition.

Hatano high (HAA)- and low (LAA)-avoidance rats were selected from Sprague-Dawley rats genetically on the basis of their active avoidance behavior in a shuttle-box test. The purpose of this study was to investigate stress-related alterations of hormones corticotropin-releasing hormone (CRH), arginine-vasopressin (AVP), prolactin, and adrenocorticotropin (ACTH) in the brain and blood during early avoidance acquisition using two lines of Hatano rats. In paraventricular nucleus (PVN) of the hypothalamus, the CRH levels in HAA rats were significantly increased after shuttle-box tasks compared with before the tasks, whereas the CRH levels in LAA rats significantly decreased after shuttle-box tasks compared with before the tasks. In the HAA rats, the CRH and AVP levels in the median eminence decreased after shuttle-box tasks, whereas there were no significant differences in the levels between before and after shuttle-box tasks in LAA rats. The plasma concentrations of ACTH were significantly higher in HAA rats than in LAA rats after shuttle-box tasks. These results show that the response of CRH-ACTH was higher in HAA rats than in LAA rats. This phenotype may be an important reason for the high avoidance rates of shuttle-box tasks in HAA rats. These endocrine differences in early avoidance acquisition may be involved in regulation of their avoidance responses in the shuttle-box task.

Endocrine mechanisms responsible for different follicular development during the estrous cycle in Hatano high- and low-avoidance rats.

Hatano high- and low-avoidance rats (HAA and LAA strains, respectively) were selected and bred according to the avoidance rate in a shuttle-box task. Although they have clear strain differences in ovarian function, their endocrine mechanisms still remain to be clarified. Differences in female reproductive endocrinology between the strains were investigated by means of measuring the plasma concentration of reproductive hormones during the estrous cycle. LAA rats showed approximately threefold lower basal and surge levels of LH, a more than fourfold lower level of FSH surges and higher levels of inhibin A and inhibin B during the estrous cycle compared with the levels seen in HAA rats. The concentration of estradiol-17ß in the proestrous stage was significantly lower in LAA rats than in HAA rats. Additionally, LH and FSH secretions from primary cultured anterior pituitary cells with or without in vitro GnRH stimulation were lower in the cells derived from LAA rats and, in terms of FSH secretion, were unresponsive to GnRH in contrast to cells derived from HAA rats. Although an increased number of preantral follicles in diestrus were observed in LAA rats, number of hCG-induced ovulation was lower in LAA rats. LAA rats may have much more follicle growth during the early stage of folliculogenesis, but most follicles might not grow into mature follicles. These results strongly suggest that the strain difference in ovarian function of these two Hatano rats is due to the difference in the regulation of hypothalamo-hypophyseal system for gonadotropins secretion.

Effect of short period vasectomy on FSH, LH, inhibin and testosterone secretions, and sperm motility in adult male rats.

The present study was undertaken to clarify changes in secretions of FSH, LH, inhibin and testosterone, and sperm motility after bilateral vasectomy in adult male rats. Bilateral vasectomy was created surgically (treated group) and intact rats were used as control (control group). On days 3, 5, 7, 14, 30, 60, and 90 after surgery, plasma concentrations of FSH, LH, inhibin, and testosterone were measured by radioimmunoassay, and sperm motility characteristics were measured by computer-assisted sperm analysis (CASA). The results show that weights of epididymides significantly increased in vasectomized rats as compared to control rats. Histologically, damage to spermatogenesis was observed in vasectomized rats. Multinucleated giant cells were observed in the lumen of some seminiferous tubules, and there were degenerative spermatids in the epididymides of vasectomized rats. Plasma levels of LH, FSH, and testosterone only decreased on day 3 after vasectomy; however, plasma levels of ir-inhibin significantly increased on day 3 after vasectomy. In addition, the sperm motility parameters, straight-line velocity, curvilinear velocity, deviation of the sperm head from the mean trajectory and the maximum amplitude of lateral head displacement were decreased from day 60 after vasectomy. These results suggest that vasectomy reduces sperm motility starting from day 60 after vasectomy, and early bilateral vasectomy does not strongly affect the endocrine function of the testis, though it may result in damage to spermatogenesis in vasectomized rats.

Effects of pantothenic acid on testicular function in male rats.

Pantothenic acid (PaA) is a water-soluble vitamin required to sustain various physiological functions in animals. The physiological roles of PaA on testicular function, in particular, testicular endocrinology and sperm mortility, were investigated in rats. Male rats at 3 weeks of age were fed a PaA-free diet or a 0.0016% PaA diet (control) for 7 weeks. Total body weight, as well as the weights of the liver, kidney, pituitary, testis, epididymis, seminal vesicle and prostate; sperm motility; and the plasma concentrations of luteinizing hormone (LH), follicle-stimulating hormone (FSH), testosterone and corticosterone were measured in rats at 10 weeks of age. Body weight gain decreased from 5 weeks of age in rats fed the PaA-free diet compared with the control. The relative weights of the testes were significantly higher in the PaA-deficient group compared with the control group. Several parameters of sperm motility were significantly reduced in the PaA-deficient group compared with the control group. In addition, the plasma concentrations of testosterone and corticosterone were significantly lower in the PaA-deficient group compared with the control group, whereas the plasma concentrations of FSH and LH showed no change. These results clearly demonstrate that PaA is an essential factor in testicular endocrinology and sperm motility in male rats.

Prolactin induces phosphorylation of the STAT5 in adrenal glands of Hatano rats during stress.

AIMS: To investigate the signaling of prolactin (PRL) in the adrenal gland during stress in Hatano high- (HAA) and low-avoidance (LAA) rats. MAIN METHODS: Adrenal glands of both strains were collected at 0, 15 and 30 min after stress. The protein levels of phosphorylated STAT5 and the mRNA levels of melanocortin receptor 2 (MC2R) and PRL receptor (PRLR) were analyzed. Furthermore, the effects of bromocriptine-induced hypoprolactinemia on adrenocortical responses to stress were investigated. KEY FINDINGS: Adrenocorticotropic hormone (ACTH) concentrations in HAA were greater than LAA, while the difference in PRL concentrations were found only at 120 min after stress induction. No strain differences were observed in corticosterone or progesterone in response to stress. The stress-induced increase in MC2R mRNA expression was higher in HAA, but there was a lowered PRLR mRNA expression. STAT5 become highly phosphorylated in response to stress in both strains, but bromocriptine led to a reduction the STAT5 phosphorylation. Exposure to bromocriptine was associated with a reduction in plasma PRL in response to stress in both strains, while the ACTH levels were not altered. However, the decrease in corticosterone and progesterone in response to stress was observed only in bromocriptine-treated LAA rats. SIGNIFICANCE: These data show that PRL plays an important role in the regulation of corticosterone and progesterone release in LAA but not in HAA during stress. These results suggest that PRL increase in response to stress, and it acts on the adrenal cortex and thereby plays an important physiologic role in protecting against acute stress.

Differences in adrenocortical secretory and gene expression responses to stimulation in vitro by ACTH or prolactin between high- and low-avoidance Hatano rats.

Rats of the Hatano high-avoidance (HAA) and low-avoidance (LAA) strains have been genetically selected on the basis of their two-way active avoidance behavior, and have different endocrine responses to stress. The present study focused on the adrenal steroid hormone responses of the Hatano strains and identifies differences in regulation of the adrenal cortex in vitro of HAA and LAA rats. Although incubation with prolactin (PRL) and/or adrenocorticotrophic hormone (ACTH) resulted in a dose-dependent increase of corticosterone and progesterone release by adrenal cells from both HAA and LAA male rats, the responses were markedly increased for adrenal cells from LAA rats as compared with HAA rats. This finding suggested that adrenal glands of HAA rats are less sensitive to PRL and/or ACTH than adrenals from LAA rats. Several possible intra-adrenal regulators were investigated. The basal level of expression of steroidogenic acute regulatory protein (StAR) and the long form of the PRL receptor (PRLR-L) mRNAs was higher in adrenals of LAA rats. ACTH treatment of adrenal cells from HAA rats resulted in statistically significant increases in melanocortin receptor 2 (MC2R) mRNA expression, while neither ACTH nor PRL altered MC2R mRNA expression in adrenal cells of LAA rats. Conversely, the increase in PRLR-L mRNA expression induced by PRL was observed only in adrenal cells from LAA rats. Treatment of adrenal cells with PRL and/or ACTH increased the expression of StAR and CYP11A1 mRNAs for both Hatano strains. However, the induction of StAR mRNA expression was higher in LAA rats, but the CYP11A1 response was lower. These findings indicate that adrenal cells of the LAA strain have higher sensitivity to secretagogues than those of the HAA strain. These results suggest that PRL may also be important in stimulating secretion of adrenal steroid hormones.

Effects of pantothenic acid supplementation on adrenal steroid secretion from male rats.

The effects of pantothenic acid-supplementation on the adrenal secretion of corticosterone and progesterone in male rats were investigated using an in vitro cell culture system. Male rats at 21 d of age were given 0.03% pantothenic acid in their drinking water for 9 weeks. After 9 weeks of treatment, the animals were decapitated, and adrenal cells were cultured in the absence or presence of rat adrenocorticotropic hormone (ACTH; 10(-15) to 10(-10) M) and/or ovine prolactin (oPRL; 10(-9) to 10(-7) M) for 4 h. Adrenal cells in pantothenic acid-treated rats exhibited higher basal levels of corticosterone and progesterone than control rats. The response of ACTH and/or PRL on corticosterone and progesterone release was higher in the pantothenic acid-treated rats than in the control rats. In addition, PRL increased the stimulatory effect of ACTH-induced corticosterone secretion in both normal and pantothenic acid-treated rats. These results clearly demonstrated that pantothenic acid supplementation stimulates the ability of adrenal cells in male rats to secrete corticosterone and progesterone. Additionally, these results also showed that pantothenic acid supplementation induced adrenal hyperresponsiveness to ACTH stimulation, and PRL further stimulated adrenal sensitivity to ACTH.