Effects of starvation and refeeding on gonadotropin and thyrotropin subunit mRNAs in male Japanese quail

The contents of mRNAs encoding LH beta-, FSH beta-, TSH beta- and common alpha-subunit precursor molecules were measured in food-deprived and subsequently re-fed male Japanese quail. Pituitary LH beta, FSH beta and common alpha mRNA levels were decreased by starvation, and increased to the control levels by re-feeding. The rates of decreases of LH beta and common alpha mRNA levels were greater the corresponding rate for FSH beta levels. Pituitary TSH beta mRNA levels were not decreased by starvation, but increased transitorily by re-feeding. Plasma LH and triiodothyronine levels were decreased by starvation, and then increased to control levels by re-feeding, while plasma FSH and thyroxine levels did not show significant changes. Plasma LH and FSH levels showed positive correlations with pituitary common alpha and FSH beta mRNA levels, respectively, while plasma thyroxine levels showed a negative correlation with TSH beta mRNA levels. Hepatic weight was decreased slightly but significantly by starvation, and then showed a remarkable rebound after re-feeding was started. These results suggest that LH synthesis and secretion are more sensitive to starvation than FSH synthesis and secretion in Japanese quail, and that LH production recovered to initial levels within several days when birds were fully fed. Also, there is a possibility that the synthesis of TSH is accelerated transitorily by re-feeding. Furthermore, these results showed that there are different relationships between the plasma levels of LH, FSH, and TSH and the various hormone subunit mRNA levels. The remarkable change in hepatic weight leads us to assume that hepatic thyroid hormone metabolism is affected by starvation and re-feeding.     

Thyroxine can mimic photoperiodically induced gonadal growth in Japanese quail

Summary Pharmacological doses of thyroxine are able to mimic the effects of long photoperiods in Japanese quail. In birds maintained on short daylengths thrice-weekly injections of 100 g thyroxine cause full testicular maturation at rates not greatly different from those seen if quail are exposed to long days. Thyroxine stimulates increases in the secretion of FSH and LH, in pituitary prolactin content and in the hypothalamic content of Gn-RH. The effects are dose-dependent. If female quail kept on short daylengths are given thyroxine their ovaries develop and they lay eggs. In castrated male quail on short days thyroxine causes a ten-fold increase in circulating LH within a week. Thyroxine injections are also capable of maintaining quail in a photorefractory state even when they are transferred to short daylengths. The results suggest that thyroxine mimics long days by acting high in the photoneuroendocrine system and does not simply act to facilitate hormone secretion per se. This is in line with growing evidence in mammals and birds that parts of the photoperiodic machinery are sensitive to thyroid hormones.Abbreviations Gn-RH gonadotropin releasing hormone - FSH follicle stimulating hormone - LH luteinizing hormone - T ₄ thyroxine     

Lithium-induced changes in the plasma and pituitary levels of luteinizing hormone,follicle stimulating hormone and prolactin in rats

Adult male Sprague-Dawley rats, maintained under a controlled photoperiod of LD 14:10 (white lights on at 06:00 h, CST), were injected with lithium chloride and changes in the levels of plasma and pituitary homogenates of luteinizing hormone (LH), follicle-stimulating hormone (FSH) and prolactin (PRL) were examined to evaluate the effects of this anti-manic drug on reproductive function. Two groups of rats were injected with lithium chloride intraperitoneally, twice daily at 09:00 and 16:00 h, for 2 and 7 days at a dosage of 2.5 meg/Kg body weight. Plasma and pituitary levels of LH, FSH and PRL were measured by radioimmunoassay. Plasma levels of LH were significantly (P<0.05) increased after 2 days of lithium treatment. In contrast, a significant (P<0.005) reduction in plasma levels of LH was evident when lithium injections were continued for 7 days. The plasma levels of FSH remained unaffected by lithium treatment by either time period. Lithium administered for 2 days did not bring about any significant alteration in the plasma levels of PRL, although there was a significant (P<0.002) reduction in plasma PRL levels after 7 days treatment. The concentrations of pituitary LH, FSH and PRL remained unchanged after 2 and 7 days of lithium treatment.     

Acute effect of thyroid hormones in mimicking photoperiodically induced release of gonadotropins in Japanese quail

Summary Photoperiodic induction occurs in Japanese quail after exposure to a single long day and this leads to a wave of pituitary LH secretion which lasts for up to 10 days. Pharmacological doses of thyroid hormones mimic this photoperiodic response if given to quail on short days, the magnitude and duration of the rise in LH and FSH output being dose-dependent. Thyroxine (T₄) is some 7 times more potent than tri-iodothyronine (T₃). There is no effect of T₄ on LH secretion in quail already on long days although such birds can increase LH output markedly if treated with Gn-RH. Testosterone prevents the initial rise in LH secretion following T₄ but does not block the long-term effect, suggesting that T₄ acts high in the photoneuroendocrine chain to mimic long days. The first rise in LH secretion following T₄ injection takes place about 24 h after the injection and the time-scale of secretion is quite similar to that seen when quail are exposed to a long day. T₄ elicits a rise in LH secretion even if the quail are maintained in darkness. However, T₄ does not act simply as light for if it is given at the exact time when birds are in a photoinducible state (i.e. 12–16 h after dawn) the rise in LH secretion still occurs 24 h later.Abbreviations FSH follicle stimulating hormone - Gn-RH gonadotropin releasing hormone - LH luteinizing hormone - T ₄ thyroxine - T ₃ tri-iodothyronine     

Differential regulation of pituitary gonadotropin subunit messenger ribonucleic acid levels in photostimulated Siberian hamsters

FSH levels begin to rise 3-5 days after male Siberian hamsters are transferred from inhibitory short photoperiods to stimulatory long photoperiods. In contrast, LH levels do not increase for several weeks. This differential pattern of FSH and LH secretion represents one of the most profound in vivo examples of differential regulation of the gonadotropins. The present study was undertaken to characterize the molecular mechanisms controlling differential FSH and LH synthesis and secretion in photostimulated Siberian hamsters. First, we cloned species-specific cDNAs for the three gonadotropin subunits: the common alpha subunit and the unique FSHbeta and LHbeta subunits. All three subunits share high nucleotide and predicted amino acid sequence identity with the orthologous cDNAs from rats. We then used these new molecular probes to examine the gonadotropin subunit mRNA levels from pituitaries of short-day male hamsters transferred to long days for 2, 5, 7, 10, 15, or 20 days. Short-day (SD) and long-day (LD) controls remained in short and long days, respectively, from the time of weaning. We measured serum FSH and LH levels by RIA. FSHbeta, LHbeta, and alpha subunit mRNA levels were measured from individual pituitaries using a microlysate ribonuclease protection assay. Serum FSH and pituitary FSHbeta mRNA levels changed similarly following long-day transfer. Both were significantly elevated after five long days (2.3- and 3.6-fold, respectively; P < 0.02) and declined thereafter, but they remained above SD control values through 20 long days. Alpha subunit mRNA levels also increased significantly relative to SD control values (maximum 2-fold increase after seven long days; P < 0.03), although to a lesser extent than FSHbeta. Neither serum LH nor pituitary LHbeta mRNA levels changed significantly following long-day transfer. The results indicate that long-day-associated increases in serum FSH levels in Siberian hamsters reflect an underlying increase in pituitary FSHbeta and alpha subunit mRNA accumulation.     

Selective failure of androgens to regulate follicle stimulating hormone beta messenger ribonucleic acid levels in the male rat

FSH beta, as well as LH beta, and alpha-subunit mRNA levels were examined in the pituitary glands of male rats after sex steroid replacement at various times (7, 28, or 90 days) after orchiectomy. Testosterone propionate, dihydrotestosterone propionate, or 17 beta-estradiol benzoate (E) were administered daily for 7 days before killing, to assess the role of different gonadal steroids on gonadotropin subunit mRNA levels. Subunit mRNAs were determined by blot hybridization using rat FSH beta genomic DNA, and alpha and LH beta cDNAs. At all time points, alpha and LH beta mRNAs increased after gonadectomy and fell toward normal levels with either androgen or estrogen replacement. FSH beta mRNA levels increased variably postcastration: 4-fold at 7 days, 2-fold at 28 days, and 4- to 5-fold at 90 days. Although E replacement uniformly suppressed FSH beta mRNAs, neither testosterone propionate nor dihydrotestosterone propionate administration suppressed FSH beta mRNA levels at any time point after orchiectomy. These data demonstrate that there is a relative lack of negative regulation of FSH beta mRNA levels by androgens in a paradigm in which E administration results in marked negative regulation of FSH beta mRNA levels. Thus, in the male rat, estrogens negatively regulate all three gonadotropin subunit mRNA levels while androgens negative regulate LH beta and alpha-subunit but fail to suppress FSH beta mRNAs.     

Inhibin, activin, and follistatin: regulation of follicle-stimulating hormone messenger ribonucleic acid levels

Primary pituitary cell cultures derived from adult male rats were used to explore the direct effects of purified porcine inhibin and follistatin, and recombinant human activin A on FSH beta, as well as LH beta and alpha-subunit mRNA levels. Subunit mRNAs were determined by blot hybridization using alpha, LH beta, and FSH beta cDNA and genomic fragments. Treatment with inhibin for 72 h significantly suppressed alpha and FSH beta mRNA levels with parallel changes in FSH secretion. No change in LH beta mRNA levels was observed. A decrease in FSH beta mRNA to undetectable levels was seen 4 h after inhibin administration. Recombinant human Activin A caused dose-dependent and parallel increases in FSH beta mRNA levels and FSH secretion. This increase was evident at 4 h after activin administration and maintained at longer times. alpha and LH beta mRNA levels remained unchanged. Follistatin addition to cultures for 72 h significantly reduced FSH beta mRNA levels. In a time-course experiment, a reduction in FSH beta mRNA to undetectable levels was observed 24 h after follistatin administration. There were no changes in alpha or LH beta mRNA levels. These data demonstrate that the actions of these gonadal peptides on FSH secretion may be accounted for, at least in part at the level of biosynthesis, by reductions in FSH beta mRNA levels directly at the level of the anterior pituitary gland.     

Relation between levels of circulating ovarian steroids and pituitary gonadotropin content during the menstrual cycle of the rhesus monkey

Anterior pituitary glands were removed from 27 intact cycling rhesus monkeys sacrificed in the early (Day 2), mid (Days 6--9) and late (Days 11--12) follicular phase, and in the early and late luteal phase (3--5 and 10--15 days after the midcycle luteinizing hormone (LH) surge). Assignment of cycle stage was confirmed by the pattern of circulating steroid and gonadotropin levels seen in the blood samples taken daily throughout the cycle. The anterior pituitary glands were weighed, stored at -30 degrees C and assayed for LH and follicle-stimulating hormone (FSH) content by specific radioimmunoassays. Serum estradiol levels and pituitary LH and FSH contents rose simultaneously during the follicular phase. After the preovulatory gonadotropin surge, pituitary LH content was low and invariant. Pituitary FSH content reached a nadir in the early luteal phase and tended to rise in the late luteal phase. Multiple correlation analyses revealed that there is a positive correlation between rising levels of estradiol in the circulation and pituitary LH (p = 0.003) and FSH (p = 0.017) content, and that there is a significant negative correlation between circulating progesterone levels and pituitary FSH content (p = 0.002). Pituitary LH content is less strongly related to circulating progesterone levels. There was no significant difference in the wet weights of the anterior pituitary glands during the five phases of the menstrual cycle studied.     

Starvation-induced suppression of pituitary-testicular function in rats is reversed by pulsatile gonadotropin-releasing hormone substitution

This study was carried out to test the hypothesis that reduced hypothalamic GnRH release is responsible for the suppression of reproductive functions during starvation. Adult male rats were kept for 4 days under total fasting (only water allowed) and injected during this time at 2-h intervals with 100 or 500 ng/kg BW of GnRH or vehicle. Serum levels of LH and FSH decreased by 30% during starvation (p less than 0.05), and these effects were fully reversed by either dose of GnRH treatment. Starvation reduced the pituitary mRNA contents of the gonadotropin common alpha- and FSH beta-subunits by 30% and 35% in starved animals (p less than 0.05 for both), but the LH beta-subunit mRNA was unaffected. The GnRH treatments partly or totally reversed these changes, but up-regulation of the mRNA levels by GnRH was seen only in controls fed ad libitum. Starvation reduced the testicular and serum levels of testosterone by 84% (p less than 0.01) and 42% (p less than 0.05), respectively. These changes were fully reversed by the 500-ng/kg dose of GnRH treatment during fasting, but only serum T was completely reversed by the 100-ng/kg GnRH treatment. To elucidate whether fasting per se had direct effects at the gonadal level, we blocked the secretion of gonadotropins by treatment with a GnRH antagonist, and replaced the gonadotropins by injecting of hCG (10 IU/kg BW once daily) and hFSH (75 IU/kg BW once daily). No differences were observed between starved and control animals in either testicular or serum levels of T, or in accessory sex gland weights.(ABSTRACT TRUNCATED AT 250 WORDS)     

More rapid restoration of pituitary content of follicle-stimulating hormone than of luteinizing hormone after depletion by oestradiol-17 beta in ewes.

To test the hypothesis that the synthesis and secretion of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) are differentially regulated after depletion by oestradiol, circulating concentrations of oestradiol were maintained at approximately 30 pg/ml for 16 days in each of 35 ovariectomized ewes. Five other ovariectomized ewes that did not receive oestradiol implants served as controls. After treatment with oestradiol, implants were removed and pituitary glands were collected from each of 5 ewes at 0, 2, 4, 8, 12, 16 and 32 days thereafter and amounts of mRNA for gonadotrophin subunits and contents of LH and FSH were quantified. Before collection of pituitary glands, blood samples were collected at 10-min intervals for 6 h. Treatment with oestradiol reduced (P less than 0.05) steady-state concentrations of LH beta- and FSH beta-subunit mRNAs and pituitary and serum concentrations of these hormones. At the end of treatment the amount of mRNA for FSH beta-subunit was reduced by 52% whereas that for LH beta-subunit was reduced by 93%. Steady-state concentrations of mRNA for FSH beta-subunit returned to control values within 2 days of removal of oestradiol, but 8 days were required for concentrations of FSH in the pituitary and serum to return to control values. Steady-state concentrations of mRNA for LH beta-subunit and mean serum concentrations of LH returned to control values by Day 8, but pituitary content of LH may require as long as 32 days to return to control levels. Therefore, replenishment of FSH beta-subunit mRNA preceded increases in pituitary and serum concentrations of FSH.(ABSTRACT TRUNCATED AT 250 WORDS)     

Thyroid function and vitamin A deficiency.

Rats, when vitamin A deficient, had increased plasma T₃, T₄ and free thyroxine indexes. Pituitary TSH and hypothalamic TRH content were increased in vitamin A deficient animals compared to pair-fed controls. The plasma TSH response to TRH was normal in the vitamin A deficient rats. Basal prolactin, LH and FSH levels did not differ significantly in the two groups. Both groups had significant increases in LH and FSH after LRH. Vitamin A deficiency produces biochemical hyperthyroidism. Our data are consistent with an abnormality in thyroid hormone feedback on the hypothalamic pituitary axis.     

Hormonal regulation of anabolic processes and of protein utilization efficiency in the early postnatal period

The levels of thyroid, pituitary and steroid hormones-thyroxine, triiodothyronine and 11-hydroxycorticosteroids in the blood serum, somatotropin in the pituitary, and processes of protein assimilation were studied in rats in the early postnatal period. The highest endogenous production of thyroxine, triiodothyronine and somatotropin was detected in 15-day-old rats. The highest level of protein utilization was detected in 7 to 15-day-old rats, followed by the lowering of the utilization on changing over to definitive nutrition. Endogenous production of the anabolic hormones thyroxine, triiodothyronine and somatotropin was found to correlate with a high level of protein utilization in rats within the first days of life after birth.     

Effects of gonadectomy and steroids on pituitary gonadotropin secretion in a frog, Rana pipiens

Secretory dynamics of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) were measured at various times following gonadectomy in adult male grass frogs, Rana pipiens. Plasma levels and in vitro initial secretory rates of both LH and FSH increased significantly within 1 wk and remained elevated for 3-4 wk of castration. Pituitary FSH and LH content were unchanged. However, dissociation between the two gonadotropins (Gth) occurred thereafter: Secretion of FSH remained elevated for 70 days, but those of LH declined to control levels after 30 days. In vitro secretion of Gth from gonadectomized (gonadx) frogs declined progressively over time reaching control levels after 24 h incubation. The results indicate that elevated pituitary secretion contributes to the observed circulating LH and FSH levels in gonadx frogs, and that FSH and LH may be controlled independently. Replacement therapy with 17 beta-estradiol (E2) suppressed post-gonadectomy increases in plasma Gth and in vitro responses to GnRH, whereas 5 alpha-dihydrotestosterone (DHT) had little effect in vivo and augmented GnRH responses in long-term castrates. In vitro, E2 also inhibited, while 48 h of DHT treatment had no effect on GnRH responsiveness of pituitaries from gonadx frogs. The actions of these steroids were opposite to those typically observed in mammals (and birds), and support the hypothesis that E2 may contribute to seasonal testicular regression in ranid frogs.     

Gonadal development and gonadotrophin secretion in the male vole (Microtus agrestis) after an abrupt change in photoperiod

Male voles were reared from birth to age 28 days in 6L:18D. Pairs of animals showing similar sexual development were assigned at random to 16L:8D or 6L:18D. Treatments continued for a further 56 days. Increase in the activity of the hypothalamo-hypophysial system occurred within 4 days of exposure to 16L:8D, as shown by significant elevation of plasma LH and FSH. Pituitary LH did not increase until Day 7, and pituitary FSH did not increase until Day 21. After exposure to 16L:8D for 4 days, pituitary FSH was lower than in corresponding animals in 6L:18D. These discrepancies between pituitary and plasma values of gonadotrophins indicate that increase in hormone release occurs before synthesis is fully stimulated. Enhanced output of testicular hormones probably began between Day 7 and Day 14, as indicated by an increase in seminal vesicle weight, yet plasma and pituitary concentrations of LH and FSH remained elevated. This suggests that long photoperiods may cause direct stimulation of the hypothalamo-hypophysial system which increasing values of testicular hormones are initially unable to inhibit. The response of this system in voles to an abrupt change from a non-stimulating to a stimulating photoperiod has a time course resembling that for the Soay ram but appreciably slower than for the Japanese quail.     

Activity of the hypothalamo-pituitary ovarian axis in hypothyroid rats with or without triiodothyronine replacement

The hypothalamic pituitary ovarian axis in adult female rats with 131-I induced hypothyroidism was studied before and after triiodothyronine (T3) replacement. Forty days after 131-I, hypothyroid (H) rats showed irregular cycles with predominantly diestrous vaginal smears, atrophied and underweight ovaries, and decreased serum T3, T4, LH and estradiol (E2). T3 replacement restored normal cycles and ovary weight and increased serum E2 levels above control values, while LH levels remained below the limit of detection of the RIA. The GnRH stimulation test performed on the day that the rats exhibited diestrous vaginal smears elicited a greater increase in FSH than in LH in H rats and a greater increase in LH than in FSH in both H-T3 treated and control rats. The data suggest that the lack of thyroid hormones in adult female rats seems to produce a reversion of sexual hormones to a prepubertal pattern, while T3 treatment restored normal estrous cycles and ovarian function.     

Androgens positively regulate follicle-stimulating hormone beta-subunit mRNA levels in rat pituitary cells

We have shown previously that androgens negatively regulate LH alpha and beta-subunit mRNA levels, but have little or no effect on FSH beta mRNA levels in rats in vivo. In contrast, estrogen negatively regulates all three gonadotropin subunit mRNA levels in vivo. We have examined the effects of these sex steroids on gonadotropin subunit synthesis directly at the level of the pituitary gland by using cultured rat pituitary cells. Adult female and male rat pituitaries were dissected, dispersed enzymatically, and maintained in culture for 2 days. At that time, cells were treated for varying lengths of time with either medium alone or sex-steroid hormone treatments (estradiol or testosterone). Dose-response and time-course experiments were performed. Cells were then harvested and total RNA was extracted. Gonadotropin subunit mRNA levels were assessed by blot hybridization techniques. Sex-steroid hormones were added to achieve final concentrations ranging from 10(-12) to 10(-6) M for dose response experiments and 10(-8) M for time-course experiments. Testosterone treatment (10(-8) M) increased FSH beta mRNA levels 3-fold in females (P less than 0.01) and males (P less than 0.05), but had no effect on alpha or LH beta mRNA levels in either sex. Dose-related increases in FSH beta mRNA levels with increasing concentrations of testosterone were observed in both female and male pituitary cell cultures. Time-course studies revealed that the testosterone-stimulated increases in FSH beta mRNA levels are statistically significant by 12 h and 6 h after hormone addition in female and male cultures, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)     

Manganese-Induced Effects on Testicular Trace Element Levels and Crucial Hormonal Parameters of Hyline Cocks

Manganese (Mn) is an essential element required for normal development and reproduction. However, little is known about the reproductive toxicity of Mn in birds. To investigate the Mn-induced toxicity on testicular trace element levels and crucial hormonal parameters on male reproduction in birds, 50-day-old male Hyline cocks were fed either a commercial diet or a Mn-supplemented diet. The changes in contents of copper (Cu), iron (Fe), zinc (Zn), and calcium (Ca) in testis were detected. Hormonal parameters were evaluated including the levels of testosterone (T), luteinizing hormone (LH), follicle-stimulating hormone (FSH), thyroid-stimulating hormone (TSH), triiodothyronine (T3), and thyroxine (T4) in the serum. The mRNA levels of luteinizing hormone receptor (LHR) and follicle-stimulating hormone receptor (FSHR) were determined in this study. The results showed that Mn was accumulated in testis, and the content of Cu, Fe, Zn, and Ca decreased. Exposure to Mn significantly lowered the content of T, LH, FSH, and the mRNA expression levels of LHR and FSHR. Levels of T3 and T4 appeared with a decreased tendency, and TSH presented no obvious regularity. It indicated that Mn exposure resulted in the disbalance of testicular trace elements and influenced hormone levels in the molecular level, which may be possible underlying reproductive toxicity mechanism induced by Mn.     

Peripheral Thyroid Hormone Dynamics in Precocial and Altricial Avian Development1

SYNOPSIS. Precocial and altricial birds have distinctly differentpatterns of general ontogeny and metabolic/thermoregulatorydevelopment. In my laboratory, we have studied the developmentof thyroid function in Japanese quail (Coturnix japonica) andRing doves (Streptopelia risoria) as examples of precocial andaltricial development, respectively. In this paper, I reviewthe literature and our work on the factors that influence peripheralhormone dynamics in birds. The first section of the paper describesadult peripheral thyroid function to set the stage for the developmentalpicture. Thyroid development is divided into two phases: PhaseI, in which the thyroid gland develops functional capacity butthere is low thyroid activity in the periphery, and Phase II,in which peripheral thyroid function increases and approachesadult levels. In precocial development Phase I occurs duringembryonic life and Phase II begins at the perinatal period.In altricial development, the pattern of thyroid functionaldevelopment is different and delayed. Peripheral thyroid hormonepatterns in both developmental modes are discussed with referenceto the factors that determine their dynamics: hormone availabilityfrom the thyroid gland, total serum hormone concentrations,the roles of serum binding proteins in regulating freehormoneconcentrations, hormone turnover and excretion, hormone receptorsand thyroid hormone metabolism, especially extrathyroidal productionof triiodothyronine from thyroxine.     

Effects of quinestrol on reproductive hormone expression, secretion, and receptor levels in female Mongolian gerbils (Meriones unguiculatus)

Quinestrol, a synthetic estrogen with marked estrogenic effects and prolonged activity, has potential as a contraceptive for Mongolian gerbils. The objective of this study was to describe the effects of quinestrol on reproductive hormone expression, secretion, and receptor levels in female Mongolian gerbils. Serum and pituitary concentrations of follicle stimulating hormone (FSH) and luteinizing hormone (LH) were decreased, whereas serum concentrations of estradiol (E2) and progesterone (P4) were increased after quinestrol treatment; the effects were both time- and dose-dependent. Furthermore, quinestrol downregulated expression of FSHβ and LHβ mRNA in the pituitary gland, as well as FSH receptor (FSHR) and estrogen receptor (ER) β in the ovary. However, it up-regulated mRNA expression levels of ERα and progesterone receptor (PR) in the pituitary gland and uterus, as well as mRNA for LH receptor (LHR) and PR in the ovary (these effects were time- and dose-dependent). In contrast, quinestrol had no significant effects on the mRNA expression levels of ERα in the ovary, or the gonadotropin α (GtHα) subunit in the pituitary gland. We inferred that quinestrol impaired synthesis and secretion of FSH and LH and that the predominant ER subtype in the pituitary gland of Mongolian gerbils may be ERα. Overall, quinestrol disrupted reproductive hormone receptor expression at the mRNA level in the pituitary-gonadal axis of the Mongolian gerbil.     

Plasma and pituitary concentrations of gonadotropins (FSH and LH) in minke whales (Balaenoptera acutorostrata) during the feeding season

This study investigated plasma and pituitary concentrations of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) and steroid hormones (progesterone: P4, testosterone:T, estradiol-17beta: E2) by enzyme-immunoassay (EIA) in minke whales (Balaenoptera acutorostrata) captured during the feeding season (December to March) in the Antarctic Ocean. Plasma FSH and LH levels in female minke whales were higher (P <0.05) than in male whales. Although the pituitary weight was not significantly different between male and female whales, pituitary FSH and LH levels were higher in females than in males (P<0.01) and mature whales than immature whales (P<0.05). Plasma levels of FSH, T and E2 were not significantly different between immature and mature male whales, but plasma LH and pituitary FSH and LH levels were higher (P<0.05) in mature than in immature whales. In both immature and mature whales regardless of gender, pituitary FSH and LH levels were correlated significantly (r=0.69: P<0.01). In mature male whales, plasma T and E2 levels (r=0.60: P<0.01), and testis weight and plasma T levels (r=0.46: P <0.05) were correlated. In immature female whales, plasma FSH and LH levels were highly correlated (r=0.68: P<0.001), but were not for mature female whales. The results show that gender and maturity influence gonadal and pituitary function of minke whales during the feeding season.