Combined effects of levonorgestrel and quinestrol on reproductive hormone levels and receptor expression in females of the Mongolian gerbil (Meriones unguiculatus)

The Mongolian Gerbil as a Useful Experimental Model in Reproductive Biology

Ultimately, the Mongolian gerbils (Meriones unguiculatus) have acquired a relevant role in biological and biomedical experiments alongside other rodents. The use of gerbils in research has been mainly oriented to physiological and pharmacological studies, with special attention to nervous, digestive, and auditory systems as well as microbiology and parasitology. Ultimately, gerbils have also been applied for studying carcinogenesis in different organs and systems, since these animals show a natural propensity to develop spontaneous proliferative lesions, especially in steroid-responsive organs. This characteristic shed light on the reproductive aspects of this rodent model regarding morphological features in male and female individuals. This review of literature summarizes the significance of this model as an alternative to the use of inbred mice and rats in reproductive experimental research, highlighting recent findings. Gerbils have contributed to the expansion of knowledge in prostate biology in male and female individuals, providing studies related to prostatic morphogenesis and neoplasia. In the testes, spermiogenesis occurs in 15 steps, differently from other experimental models. Also, the complete maturation of the testis-epididymal complex occurs between the second and third months. Mammary gland alterations related to the estrous cycle and pregnancy were described, as well as its modulation under endogenous and exogenous estrogenic compounds. The ovaries frequently present ovarian cysts. Furthermore, this organ shows predominantly interstitial steroidogenic glands in the stroma, especially at aging. Adrenal gland shows a large size compared to other animals, presenting three distinct zones with a remarkable role in steroidogenesis.

Impact of contraceptive hormones on the reproductive potential of male and female commensal black rats (Rattus rattus)

The black rat is considered one of the world's top pests. With increased restrictions on rodenticides, new alternatives to manage rats are urgently needed. Research on the use of contraceptive hormones, levonorgestrel (LE), and quinestrol (QU), have been evaluated against some rodent species, and this research is the first study to assess these on black rats. Hormones were incorporated into rodent bait at 10 and 50 ppm concentrations singly and in combination (EP-1). Groups of 10 animals of each sex were fed the baits over 7 days. Lower bait consumption was observed with slight body mass reductions. On dissection, it was observed that the uterus was in a state of edema and male reproductive organs weighed less with reduced sperm counts/motility. The 2 most promising baits, 50 ppm QU and EP-1, were used to assess impact on pregnancy and litter size. Pregnancy was reduced from 70% success when both males and females consumed untreated bait, down to 30% when males had consumed contraceptive bait but females had not, and down to 0% when females had consumed contraceptive bait, regardless of whether they had paired with a treated or untreated male. Litter size in the untreated pairs was 8 pups, but only 4 pups in those cases where the male only had consumed the contraceptive. Further studies should investigate how long the effect lasts and its reversibility. Field studies at the population level may also shed light on the practicality of using contraceptive baits for black rats in different habitats.

Prenatal and pubertal exposure to 17α-ethinylestradiol disrupts folliculogenesis and promotes morphophysiological changes in ovaries of old gerbils (Meriones unguiculatus)

17α-Ethinylestradiol is an endocrine-disrupting chemical that make up most contraceptive pills and can be found in the environment. Exposure to ethinylestradiol in different development periods may promote changes in morphophysiological parameters of reproductive and endocrine organs. Considering that the effects of low doses (15 µg/kg/day) of ethinylestradiol in ovaries from 12-month-old female gerbils (Meriones unguiculatus) were investigated. Four experimental groups used were control (without treatment), EE/PRE (treated from the 18th to the 22nd gestational day), EE/PUB (treated from the 42nd to the 49th day of life), and EE/PRE-PUB (treated in the both periods). The animals were euthanized at 12 months. Testosterone and 17β-estradiol levels were measured. The ovaries were stained with Hematoxylin and Eosin, Periodic Acid Schiff, and Gomori's Trichome. The follicles, corpus luteum, interstitial gland, lipofuscin, ovarian epithelium, and tunica albuginea were analyzed. Estradiol was higher in EE/PRE and EE/PUB groups, while testosterone was higher only in EE/PUB group. The main changes in follicle count occurred in EE/PUB and EE/PRE-PUB groups, with higher primordial follicle count and lower maturation of follicles. The corpus luteum was more evident in EE/PRE group. No differences were found in atretic follicles count. A higher area occupied by interstitial gland cells and lipofuscin deposit in these cells was noted in EE/PUB and EE/PRE-PUB groups. Higher epithelium height and thicker tunic albuginea were showed in treated groups. These results suggest that exposure to doses of EE2 in prenatal and pubertal periods of the development leads to morphological changes in senile ovaries.

The reproductive inhibitory effects of levonorgestrel, quinestrol, and EP-1 in Brandt's vole (Lasiopodomys brandtii)

Background

Rodent pests can inflict devastating impacts on agriculture and the environment, leading to significant economic damage associated with their high species diversity, reproductive rates and adaptability. Fertility control methods could indirectly control rodent pest populations as well as limit ecological consequences and environmental concerns caused by lethal chemical poisons. Brandt’s voles, which are common rodent pests found in the grasslands of middle-eastern Inner Mongolia, eastern regions of Mongolia, and some regions of southern Russia, were assessed in the present study.

Methods

We evaluated the effects of a 2-mg/kg dose of levonorgestrel and quinestrol and a 1:1 mixture of the two (EP-1) on reproductive behavior as well as changes in the reproductive system, reproductive hormone levels, and toxicity in Brandt’s voles.

Results

Our results revealed that all three fertility control agents can cause reproductive inhibition at a dosage of 2 mg/kg. However, quinestrol caused a greater degree of toxicity, as determined by visible liver damage and reduced expression of the detoxifying molecule CYP1A2. Of the remaining two fertility control agents, EP-1 was superior to levonorgestrel in inhibiting the secretion of follicle-stimulating hormone and causing reproductive inhibition. We believe that these findings could help promote the use of these fertility control agents and, in turn, reduce the use of chemical poisons and limit their detrimental ecological and environmental impacts.

Impact of Cold Exposure on the Reproductive Function in Female Rats

Female reproductive system diseases caused by exposure to a cold environment are widely considered as important human health challenges. Although the projection of female reproduction in cold temperature has been studied, a holistic view on the probable effects of cold exposure on the functions of the female reproductive system has not been achieved. Our aim was to evaluate the effects of cold exposure to the functions of the ovary and uterus in female rats. For this purpose, female rats were randomly grouped as follows: (1) the cold group was exposed to -10°C, 4 h per day for 2 weeks, and (2) the normal temperature (23 ± 1°C) group was used as control. Alterations were observed in different parameters, including body weight gain, organ coefficients, estrus cycle, and pathology of the cold-exposed female rats. Similarly, the serum reproductive hormones and mRNA expression were evaluated. Cold exposure induced estrus cycle irregularity and some alterations in the morphology of the ovary. Cold exposure impairs the function of the ovary probably by changing the level of serum LH and increasing LHR expression. Cold exposure induced a significant reduction of uterine epithelium height. Cold exposure causes alterations in the morphology of the uterus probably because of the effect of progesterone, the increase in the PR level, and the decrease in the ER level.

Effect of synthetic hormones on reproduction in Mastomys natalensis

Rodent pest management traditionally relies on some form of lethal control. Developing effective fertility control for pest rodent species could be a major breakthrough particularly in the context of managing rodent population outbreaks. This laboratory-based study is the first to report on the effects of using fertility compounds on an outbreaking rodent pest species found throughout sub-Saharan Africa. Mastomys natalensis were fed bait containing the synthetic steroid hormones quinestrol and levonorgestrel, both singly and in combination, at three concentrations (10, 50, 100 ppm) for 7 days. Consumption of the bait and animal body mass was mostly the same between treatments when analysed by sex, day and treatment. However, a repeated measures ANOVA indicated that quinestrol and quinestrol + levonorgestrel treatments reduced consumption by up to 45%, particularly at the higher concentrations of 50 and 100 ppm. Although there was no clear concentration effect on animal body mass, quinestrol and quinestrol + levonorgestrel lowered body mass by up to 20% compared to the untreated and levonorgestrel treatments. Quinestrol and quinestrol + levonorgestrel reduced the weight of male rat testes, epididymis and seminal vesicles by 60-80%, and sperm concentration and motility were reduced by more than 95%. No weight changes were observed to uterine and ovarian tissue; however, high uterine oedema was observed among all female rats consuming treated bait at 8 and 40 days from trial start. Trials with mate pairing showed there were significant differences in the pregnancy rate with all treatments when compared to the untreated control group of rodents.

Actions of oestradiol and progesterone on the prostate in female gerbils: reversal of the histological effects of castration

The female prostate is a functionally active gland in several mammalian species, including humans and rodents. Investigations of prostate morphophysiology during the phases of the oestrous cycle have shown that the female prostate is influenced by fluctuations in serum concentrations of oestradiol (E2) and progesterone (P4). The aim of the present study was to evaluate the effect of combined prolonged administration of E2 and P4 on the prostate in ovariectomised female gerbils. Ovariectomy caused atrophy and decreased glandular secretory activity. Administration of E2 and P4 (0.1mgkg(-1) diluted in 0.1mL of mineral oil, every 48h over 30 days) resulted in a recovery of overall prostate structure, as evidenced by increased epithelial height, mass and prostatic secretory activity, without leading the appearance of significant lesions. Evaluation of androgen receptor (AR) expression revealed increased immunoreactivity in the E2+P4-treated group. Immunostaining for oestrogen receptor (ER) α was decreased in the castrated groups, but increased in the group subjected to hormone treatment. There were no significant differences in ERβ immunoreactivity among the groups. Assessment of cell proliferation revealed greater immunoreactivity in the treated group. Together, the results indicate that the interaction between E2 and P4 may be responsible for maintaining female prostate gland histophysiology.

Resumption of ovarian function after 4 years of estro-progestin treatment in a young woman with Crohn's disease and premature ovarian insufficiency: a case report

PURPOSE

To report the long-term management of a case of premature ovarian insufficiency of unknown origin in a young woman with Crohn's disease.

METHOD

Here is reported the case of a 20 years old woman with Crohn's disease presenting with two years amenorrhea and FSH and LH levels of 255 mIU/ml and 182 mIU/ml respectively, who received 10 months corticosteroid treatment followed by 7 years of estro-progestin treatment.

RESULTS

Corticosteroid treatment was ineffective in restoring patients gonadotropin levels as well as ovarian volume, while estro-progestins promoted a prompt reduction in gonadotrophin levels, which returned in the normal range after two years of treatment, as well as restoration of ovarian function, which occurred after four years of estrogens administration, as demonstrated by normal ovarian volume and ovulatory follicles at ultrasound, and by the re-establishment of regular menses after estroprogestin discontinuation.

CONCLUSIONS

Long-term suppression of the endogenous gonadotropins using estroprogestins may be suggested as a treatment able to restore ovarian responsiveness even in patients with premature ovarian insufficiency showing highly elevated gonadotropin levels.