Circulating hormone concentrations in hypothyroid rats with induced polycystic ovaries

The induction of polycystic ovaries in hypothyroid rats by human chorionic gonadotropin (hCG) has been studied for many years. A complete understanding of this phenomenon requires information regarding the circulating levels of the hormones of the hypophyseal-gonadal axis. In this study, serum prolactin (PRL), luteinizing hormone (LH), estradiol, testosterone, and progesterone were measured by radioimmunoassay at intervals during the 40-day period in which large ovarian cysts were induced in hypothyroid rats by daily injections of hCG. After 20 injections, ovaries increased in weight 10-fold, and well-developed ovarian cysts were present, accompanied by lutein tissue; cyst development continued for the subsequent 20 days of hCG. Both PRL and LH rose during the first 5 days of treatment and were maintained at high levels from day 20 on. The pattern of change of gonadal steroids showed greater increases with hCG in hypothyroid than in euthyroid rats. Levels of estradiol in hypothyroid, hCG-injected rats increased in parallel to ovarian hypertrophy, whereas progesterone was high in initial stages and then declined. Testosterone increased in both euthyroid and hypothyroid animals, with no clear pattern coincident with cyst formation. The data suggest that the formation of polycystic ovaries in the hypothyroid rat is associated with high levels of PRL and LH followed by elevations of estradiol, which may serve to maintain continuous PRL, as well as LH, stimulation of the ovary.     

Comparison of the effects of human chorionic gonadotropin and luteininzing hormone on phosphofructokinase activity in isolated rat ovaries.

Phosphofructokinase activity in prepubertal rat ovaries is elevated by in vitro treatment with human chorionic gonadotropin or luteinizing hormone. The stimulatory effects of the two gonadotropins are additive. Puromycin and actinomycin D do not affect the enzyme increase induced by human chorionic gonadotropin, but the stimulatory action of luteinizing hormone is completely abolished by these antibiotics. These data suggest that the two hormones have different mechanisms of action and probably occupy different receptor sites on the ovarian cells.     

Formation of ovarian follicular cysts and corpora lutea after treatment with antihistamine or indomethacin in prepubertal gilts

Roles of histamine and prostaglandins in the induction of ovarian cysts after unilateral ovarian manipulation (MAN) and in the process of ovulation were evaluated in prepubertal gilts treated with pregnant mare's serum gonadotropin (PMSG) and human chorionic gonadotropin (hCG). Administration of pyrilamine maleate, an H1 receptor antagonist, before MAN or hCG injection reduced the number of cysts formed but did not alter ovulation rate. Administration of cimetidine, an H2 receptor antagonist, failed to alter the incidence, number, or diameters of cysts formed in response to MAN or the ovulation rate on non-MAN ovaries. Administration of indomethacin, an inhibitor of prostaglandin synthesis, before MAN or hCG injection did not alter the incidence, number, or diameters of cysts formed on MAN ovaries but reduced the number of corpora lutea on non-MAN ovaries. Excessive accumulation of fluid in ovarian cysts apparently was mediated by histamine interacting with the H1-type receptor. Enhanced secretion of prostaglandins produced by the cyclooxygenase pathway did not contribute to development of ovarian cysts but, unlike histamine, was required for formation of corpora lutea in prepubertal gilts treated with PMSG and hCG.     

Tachykinins in the normal and gonadotropin-stimulated ovary of the mouse

In this investigation, substance P (SP) and neurokinin A (NKA) concentrations have been determined in the ovary of control prepubertal mice, and prepubertal mice injected with pregnant mare serum (PMS) gonadotropin, an equine gonadotropin with predominant FSH action, or with PMS followed by human chorionic gonadotropin (hCG), which produces heavily luteinized ovaries after the stimulation with PMS. Control animals were injected with saline. The ovaries of animals treated with gonadotropins were heavier than the control ovaries, the combination of PMS plus hCG produced significantly heavier ovaries than PMS alone. The concentrations of SP and NKA in the ovaries of the animals treated with PMS or PMS/hCG were significantly lower than in control ovaries. No significant differences in ovarian tachykinin concentrations were observed between PMS and PMS/hCG-treated animals. The total ovarian content of SP was lower in PMS-injected animals as compared with the controls. The total ovarian content of NKA was not significantly different in the three groups of animals studied. These results show that ovaries stimulated with gonadotropins have lower concentrations of tachykinins than normal ovaries at the same age. It is therefore evident that gonadotropins can affect tachykinin stores in the ovaries of mice.     

Ultrasonographic characterization of the ovaries in non-pregnant first served sows and gilts

This study was aimed firstly, to examine the ovaries in non-pregnant first served sows and gilts by transcutaneous ultrasonography and secondly, to evaluate the suitability for this procedure to be performed routinely on farms. Two thousand five hundred and twenty-three females on a 1250-sow unit, synchronized with Regumate (gilts only) and/or gonadotropins (sows and gilts) not detected as returned to estrus by daily boar contact prior to scanning were ultrasonographically tested for pregnancy between days 20 and 114 postinsemination (p.i.). Of 256 sows (S) and 130 gilts (G) found to be non-pregnant the ovaries were visualized in 87.1 and 80.0% of them, respectively. Ovarian findings were: corpora lutea (CL); follicles of 2-6mm (F(2-6)); peri-ovulatory ovarian structures (POS; comprising follicles of 7-8mm and corpora haemorrhagica); single cysts (SC); oligocystic ovarian degeneration (OOD) and polycystic ovarian degeneration (POD). Their incidence was: CL>F2-6>POS>POD ( P<0.05 ) in both S and G. POD and SC plus OOD were more frequently in S ( P<0.05 ). The ovarian findings were related to the intervals of regular (days 18-25 p.i. (R1), 38-46 p.i. (R2)) and irregular service returns (days 26-37 p.i. (IR1), 47-114 p.i. (IR2)). Comparison within intervals: CL tended to be more frequently with P<0.05 only at IR2 in S. Comparison among intervals (R1 to IR2): The percentage of females (1) with CL tended to increase (S and G) and (2) with F2-6 plus POS decreased significantly (S; P<0.05 ) or tendentiously (G). SC plus OOD was higher before R2, POD after IR1 (S and G; P<0.05 ). In conclusion, the results indicate a high heterogeneity of ovarian structures in non-pregnant first served sows and gilts up to day 114 after service and suggest CL as an important cause for a delayed and, rather than POD, a failed service return. The results further demonstrate that transcutaneous ultrasonography is an appropriate and recommended method for examining the ovaries on farm in female pigs with reproductive failures.     

Hormonal changes during the early development of ovarian cysts in the rat

The daily administration of human chorionic gonadotropin (hCG) to rats with thiouracil-induced hypothyroidism results in the development of cystic ovaries. This study was undertaken to delineate hormonal changes during the first 48 h of hCG treatment. Groups of euthyroid and hypothyroid rats were injected daily with hCG or saline for up to two days and killed at 0, 12, 24, or 48 h after the initial hCG injection. Sera were analyzed for progesterone (P), testosterone (T), 17 beta-estradiol (E2), and prolactin (Prl) by specific radioimmunoassay (RIA). Serum levels of these hormones were not significantly different in the euthyroid and hypothyroid rats. However, P was significantly elevated at 12, 24, and 48 h in the hypothyroid/hCG rats. T and Prl were significantly elevated at 12 and 48 h in the hypothyroid/hCG rats. T levels were also elevated at 12 and 48 h in the euthyroid rats receiving hCG. In contrast, hCG had no effect on P and Prl levels in the euthyroid rats. E2 levels were undetectable in the euthyroid and hypothyroid rats. The administration of hCG increased E2 in both the euthyroid and hypothyroid rats at 48 h with significantly more E2 detected in the hypothyroid rats. These results show that ovarian steroids and Prl levels increase during the early stages of cyst induction and suggest they may be important in triggering ovarian cyst formation.     

Upregulation of Slc39a10 gene expression in response to thyroid hormones in intestine and kidney

A novel zinc transporter has been purified and cloned from rat renal brush border membrane. This transporter was designated as Zip10 encoded by Slc39a10 gene and characterized as zinc importer. Present study documents the impact of thyroid hormones on the expression of Zip10 encoded by Slc39a10 gene in rat model of hypo and hyperthyroidism. Serum T₃ and T₄ levels were reduced significantly in hypothyroid rats whereas these levels were significantly elevated in hyperthyroid rats as compared to euthyroid rats thereby confirming the validity of the model. Kinetic studies revealed a significant increase in the initial and equilibrium uptake of Zn⁺⁺ in both intestinal and renal BBMV of hyperthyroid rats in comparison to hypothyroid and euthyroid rats. By RT-PCR, Slc39a10 mRNA expression was found to be significantly decreased in hypothyroid and increased in hyperthyroid as compared to euthyroid rats. These findings are in conformity with the immunofluorescence studies that revealed markedly higher fluorescence intensity at periphery of both intestinal and renal cells isolated from hyperthyroid rats as compared to hypothyroid and euthyroid rats. Higher expression of Zip10 protein in hyperthroid group was also confirmed by western blot. These findings suggest that expression of zinc transporter protein Zip10 (Slc39a10) in intestine and kidney is positively regulated by thyroid hormones.     

Elements in erythrocytes of population with different thyroid hormone status

The contents of elements K, Ca, Fe, Cu, Zn, Se, and Rb in erythrocytes of 78 cases with different thyroid hormone status have been measured by proton-induced X-ray emission and neutron activation analysis. According to the status of thyroid hormones T₃, T₄, TSH, FT₃, and FT₄ detected by radioimmunoassay, the experiment subjects were divided into four groups (i.e., hyperthyroid, hypothyroid, critical [one of thyroid hormones was abnormal], and normal). Elements contents and hormones levels of four groups were analyzed by one-way analysis of variance and correlation using an SPSS/PC statistical package. The results showed that the Se contents of four groups were not significantly different (p<0.05). Zn content of hypothyroid group was significantly higher than those of hyperthyroid and critical groups. The Zn content of the normal group was higher than that of the hypothyroid group and lower than that of the hyperthyroid and critical groups. In the hyperthyroid group, there were significant correlations between elements contents and thyroid hormones levels (except TSH), but not between elements contents and levels of thyroid hormones. However, in the hypothyroid group, relatively strong correlations have been found between elements contents and thyroid hormones levels, especially between Zn and the T₃/T₄ ratio, and between Zn and TSH.     

The effect of luteinizing hormone, human chorionic gonadotropin and adrenocorticotropic hormone on puberty in gilts reared in confinement

Three trials were conducted to determine the effect of human chorionic gonadotropin (HCG), luteinizing hormone (LH) and adrenocorticotrophic hormone (ACTH) on the incidence of estrus in gilts which were reared in confinement, relocated and exposed to a boar. In trial 1, 33 gilts were given saline or 250 IU HCG at an average age of 191 days and then relocated and observed for estrus twice daily for 10 days. Treatment with HCG did not increase the proportion of gilts that exhibited estrus. In trial 2, 42 gilts were relocated at an average age of 200 days. The gilts were assigned to three treatment groups and injected with saline, 68 mug LH or 1 mg LH. After 10 days of estrous detection, a laparoscopic examination of the ovaries was conducted on all gilts failing to exhibit estrus. In groups 1 to 3, the proportions of gilts exhibiting estrus or ovulating during the 10 days after treatment were 13 of 21, 6 of 10, and 5 of 11, respectively. In trial 3, 12 gilts were relocated to pasture lots, given saline or 80 IU ACTH twice daily for 2 days and checked for estrus for 14 days. The proportions of gilts that exhibited estrus after the administration of saline or ACTH were 4 of 6 and 6 of 6, respectively. The results indicate that the incidence of estrus in gilts reared in confinement, relocated and exposed to a boar was not affected by pre-treatment with exogenous HCG, LH or ACTH.     

Pituitary and ovarian hormone secretion and ovulation in gilts injected with gonadotropins during and after oral administration of progesterone agonist (Altrenogest)

We determined changes in plasma hormone concentrations in gilts after treatment with a progesterone agonist, Altrenogest (AT), and determined the effect of exogenous gonadotropins on ovulation and plasma hormone concentrations during AT treatment. Twenty-nine cyclic gilts were fed 20 mg of AT/(day X gilt) once daily for 15 days starting on Days 10 to 14 of their estrous cycle. The 16th day after starting AT was designated Day 1. In Experiment 1, the preovulatory luteinizing hormone (LH) surge occurred 5.6 days after cessation of AT feeding. Plasma follicle-stimulating hormone (FSH) increased simultaneously with the LH surge and then increased further to a maximum 2 to 3 days later. In Experiment 2, each of 23 gilts was assigned to one of the following treatment groups: 1) no additional AT or injections, n = 4; 2) no additional AT, 1200 IU of pregnant mare's serum gonadotropin (PMSG) on Day 1, n = 4); 3) AT continued through Day 10 and PMSG on Day 1, n = 5, 4) AT continued through Day 10, PMSG on Day 1, and 500 IU of human chorionic gonadotropin (hCG) on Day 5, n = 5; or 5) AT continued through Day 10 and no injections, n = 5. Gilts were bled once daily on Days 1-3 and 9-11, bled twice daily on Days 4-8, and killed on Day 11 to recover ovaries. Termination of AT feeding or injection of PMSG increased plasma estrogen and decreased plasma FSH between Day 1 and Day 4; plasma estrogen profiles did not differ significantly among groups after injection of PMSG (Groups 2-4). Feeding AT blocked estrus, the LH surge, and ovulation after injection of PMSG (Group 3); hCG on Day 5 following PMSG on Day 1 caused ovulation (Group 4). Although AT did not block the action of PMSG and hCG at the ovary, AT did block the mechanisms by which estrogen triggers the preovulatory LH surge and estrus.     

The atrial natriuretic peptide- and catecholamine-induced lipolysis and expression of related genes in adipose tissue in hypothyroid and hyperthyroid patients

Thyroid dysfunction is associated with several abnormalities in intermediary metabolism, including impairment of lipolytic response to catecholamines in subcutaneous abdominal adipose tissue (SCAAT). Atrial natriuretic peptide (ANP) is a powerful lipolytic peptide; however, the role of ANP-mediated lipolysis in thyroid disease has not been elucidated. The aim of this study was to investigate the role of thyroid hormones in the regulation of ANP-induced lipolysis as well as in the gene expression of hormone-sensitive lipase, phosphodiesterase 3B (PDE3B), uncoupling protein-2 (UCP2), natriuretic peptide receptor type A, and beta(2)-adrenergic receptor in SCAAT of hyperthyroid and hypothyroid patients. Gene expression in SCAAT was studied in 13 hypothyroid and 11 hyperthyroid age-matched women before and 2-4 mo after the normalization of their thyroid status. A microdialysis study was performed on a subset of nine hyperthyroid and 10 hypothyroid subjects. ANP- and isoprenaline-induced lipolyses were higher in hyperthyroid subjects, with no differences between the groups following treatment. Hormone-sensitive lipase gene expression was higher in hyperthyroid compared with hypothyroid subjects before treatment, whereas no difference was observed following treatment. No differences in gene expression of other genes were observed between the two groups. Following treatment, the gene expression of UCP2 decreased in hyperthyroid, whereas the expression of PDE3B decreased in hypothyroid subjects. We conclude that thyroid hormones regulate ANP- and isoprenaline-mediated lipolysis in human SCAAT in vivo. Increased lipolytic subcutaneous adipose tissue response in hyperthyroid patients may involve postreceptor signaling mechanisms.     

Gonadotropins increase concentrations of immunoreactive insulin-like growth factor-I in porcine follicular fluid in vivo

To evaluate the regulation of ovarian insulin-like growth factor-I (IGF-I) during follicular growth in vivo, we measured the concentration of this peptide in follicular fluid (FFL) of immature gilts during the induction of follicular development by pregnant mare's serum gonadotropin (PMSG) and human chorionic gonadotropin (hCG). FFL concentrations of immunoreactive (i) IGF-I were compared with those of intrafollicular steroids and with concentrations of iIGF-I, estradiol (E2), and porcine growth hormone (GH) in serum. PMSG, administered at Time 0, induced a significant (p less than 0.01), time-dependent increase in intrafollicular iIGF-I that peaked 72 h after administration of the hormone, before the administration of hCG. During the first 72 h, the changes in ovarian iIGF-I paralleled those for progesterone and E2. After the administration of hCG at 72 h, FFL levels of E2 fell, those of iIGF-I remained constant, and progesterone rose. Serum E2 concentrations paralleled those in FFL. Since serum GH and IGF-I levels rise during spontaneous puberty in some species, these levels were also monitored. However, a significant treatment effect on serum GH and iIGF-I was not demonstrated. In summary, ovarian concentrations of iIGF-I are increased by gonadotropic hormones in vivo. The absence of concomitant changes in circulating levels of iIGF-I and GH suggests that the gonadotropin effects are exerted directly on the ovary. These results, together with more abundant data regarding secretion and action of IGF-I in cultured granulosa cells, suggest that IGF-I may function in an autocrine or paracrine fashion to amplify the actions of gonadotropins at an ovarian level.     

Ovarian development in Meishan pigs

Ovaries collected from a total of 35 Meishan gilts of various ages were morphologically and histologically examined. Vesicular follicles were first observed in ovarian sections at 45 d of age. Simultaneously, protruding follicles appeared on the surface of the ovaries, and then ovarian weight increased rapidly with an increasing number of protruding follicles. About half of the gilts between 75 and 90 d of age had ovaries with corpora lutea, indicating that some of them had started estrous cycles before reaching 75 d of age. In Meishan gilts treated with exogenous gonadotropins, ovaries were stimulated as early as 45 d of age. These results suggest that the precocity of Meishan gilts may include the development of vesicular follicles in the ovaries at an early age.     

The effect of experimental, long-term exposure to low-dose zearalenone mycotoxicosis on the histological condition of ovaries in sexually immature gilts

Farm animals are at risk of exposure to zearalenone (ZEA) in feedstuffs, which may lead to aberrations in their reproductive development, thereby adversely affecting production outcomes. The objective of this study was to determine the effect of long-term (48 days), per os administration of low ZEA doses (50% [20 μg ZEA/kg body weight (bw)] and 100% [40 μg ZEA/kg bw] NOAEL values) on anatomopathological changes in the ovaries of sexually immature gilts. The experiment involved 12 clinically healthy gilts aged 2 months with an initial body weight of about 40 kg and a determined immune status. The animals were randomly divided into two experimental groups (E1, E2) and a control group (C; all n = 4). Group E1 received per os 20 μg ZEA/kg bw for 48 days; group E2 received per os 40 μg ZEA/kg bw for 48 days; and group C received per os placebo for 48 days. Analytical samples of the mycotoxin were administered daily per os in gelatine capsules before morning feeding. Animals were sacrificed at the end of the experiment. The results of anatomopathological examinations of the ovaries in immature gilts subjected to long-term, low-dose ZEA exposure showed that ZEA-induced experimental hyperoestrogenism lowered the proliferative ability of granulosa cells of the ovarian follicle walls and of the connective tissue of the ovarian stroma, in particular at the lower ZEA dose.     

Role of the tidal cycle in the gonadal development and spawning of the tropical wrasse Halichoeres trimaculatus

Many wrasses on coral reefs exhibit daily spawning that peaks around daytime high tides. In this study, we examined tidal-related ovarian development in the threespot wrasse, Halichoeres trimaculatus, a species common on coral reefs in the Indo-Pacific Ocean. When the fish were collected in the morning at different tidal phases, the gonadosomatic index (GSI) and ovarian histology changed; concomitant with increases in GSI towards high tide, a clutch of the most advanced oocytes developed from vitellogenic to maturation stages. Ovulated eggs and post-ovulated follicles (POF) existed in most ovaries around high tide, but only POF remained around ebb tide, suggesting that spawning occurred during or after high tide. We noticed that tidal-related spawning was considerable in the morning and that most ovaries collected on the afternoon high tide exhibited post-spawning features. This suggests that certain labrid species possess plasticity with regard to their spawning time and utilize potent environmental cues to ensure their reproductive success. When pieces of ovary were incubated with precursor steroids, high conversion of testosterone to 17beta-estradiol occurred during high and ebb tides, while that of 17alpha-hydroxyprogesterone to 17alpha,20beta-dihydroxy-4-pregnen-3-one and 17alpha,20beta,21-trihydroxy-4-pregnen-3-one was observed during low and flood tides. Incubation of pieces of ovary with human chorionic gonadotropin resulted in similar fluctuations in the steroid hormones with tidal phase. Production of these steroid hormones correlated with oocyte development in the ovaries and was probably regulated by gonadotropin. These results demonstrate that the daily cycle is fundamental for oocyte development, and that the tidal cycle is superimposed on this process.     

Upregulation of Slc39a10 gene expression in response to thyroid hormones in intestine and kidney

A novel zinc transporter has been purified and cloned from rat renal brush border membrane. This transporter was designated as Zip10 encoded by Slc39a10 gene and characterized as zinc importer. Present study documents the impact of thyroid hormones on the expression of Zip10 encoded by Slc39a10 gene in rat model of hypo and hyperthyroidism. Serum T(3) and T(4) levels were reduced significantly in hypothyroid rats whereas these levels were significantly elevated in hyperthyroid rats as compared to euthyroid rats thereby confirming the validity of the model. Kinetic studies revealed a significant increase in the initial and equilibrium uptake of Zn(++) in both intestinal and renal BBMV of hyperthyroid rats in comparison to hypothyroid and euthyroid rats. By RT-PCR, Slc39a10 mRNA expression was found to be significantly decreased in hypothyroid and increased in hyperthyroid as compared to euthyroid rats. These findings are in conformity with the immunofluorescence studies that revealed markedly higher fluorescence intensity at periphery of both intestinal and renal cells isolated from hyperthyroid rats as compared to hypothyroid and euthyroid rats. Higher expression of Zip10 protein in hyperthyroid group was also confirmed by western blot. These findings suggest that expression of zinc transporter protein Zip10 (Slc39a10) in intestine and kidney is positively regulated by thyroid hormones.     

Influence of thyroid states on stress gastric ulcer formation

Thyroid hormones exert a critical developmental and regulatory role on the morphology and biochemistry of gastrointestinal mucosal cells. However, the relationship between thyroid function and stress gastric lesion formation remains undetermined. This study was designed to test the hypothesis that thyroid states may affect the acute development of gastric lesions induced by cold-restraint stress. Normal (euthyroid), hyperthyroid (200 micrograms of T4 i.p. x 7 days) and hypothyroid (thyroidectomized) rats were used. Gastric lesion incidence and severity was significantly (p less than 0.05) increased in hypothyroid rats, whereas in contrast hyperthyroid rats developed significantly less gastric lesions. As anticipated, plasma levels of thyroxin (T4) were significantly (p less than 0.01) elevated in hyperthyroid rats, and undetectable in hypothyroid rats. Acute pretreatment with i.p. cimetidine (100 mg/Kg), but not T4 (200 micrograms/Kg) 1 h prior to stress completely prevented gastric lesions formation in hypothyroid rats. Finally, binding of 3H-dihydroalprenolol to beta-adrenergic receptors on brain membranes prepared from frontal cortex was reduced by 20% in hypothyroid rats after 3 h of stress. These and other data contained herein suggest that thyroid hormones contribute to modulate the responsiveness of the gastric mucosa to stress. The increased rate of ulcerogenesis observed in hypothyroid rats appears to be mediated by gastric acid secretion. The central mechanism of this response may involve decreased brain nonadrenergic receptor function.     

Clinical,Morphological and Endocrinological Studies in Gilts with Delayed Puberty

Thirty-six gilts which had not shown oestrus at about 8 months of age or more were transported from the pig research station to the clinic, a journey of 12 km. The gilts were examined by laparoscopy and those which had only small follicles in the ovaries were catheterized and placed in pens, with sexually mature boars kept in adjacent pens. Oestrus detection was done twice daily and blood was sampled three times a day. After 7 days the laparoscopy was repeated and gilts which still had only small follicles in their ovaries were given 250 μg GnRH intravenously the following day. Blood samples were taken frequently before and after GnRH treatment. One week. after administration of GnRH the ovaries were inspected by laparoscopy once more. The first laparoscopic examination showed that 42 % of the gilts were sexually mature. One gilt had no uterus or ovaries. Twenty gilts had only small follicles in the ovaries and fourteen of these gilts showed ovulatory oestrus 5.5 days (4-7.5 days) after arrival. In these fourteen gilts a rise in the oestradiol-17B level (>30 pmol/1) was seen at an average time of 1.9 days and a rise in LH (preovulatory peak) was seen at an averaged 4.5 days after the start of blood sampling. Six gilts were given 250 ug GnRH. An immediate rise in LH could be seen in all the gilts (mean peak level was 6.18 μg/l) and the elevated levels had a duration of 4 hours. None of the GnRH-treated gilts responded with oestrus symptoms or increased ovarian activity.