Aging effects in adrenal cortex of male Mongolian gerbil: A model for endocrine studies.

The adrenal gland produces steroid hormones that act in the homeostasis of organisms. During aging, alterations in the hormonal balance affect the adrenal glands, but these have not yet been fully described due to the lack of adequate animal models. The adrenal gland of the Mongolian gerbil has a morphology similar to the primate's adrenal gland, which makes it a possible animal model for endocrine studies. Therefore, the current study aimed to study the morphophysiology of the adrenal gland under the effect of aging. For this purpose, males Meriones unguiculatus, aged three, six, nine, twelve, and fifteen months were used. Morphometric, immunohistochemical, and hormonal analyses were performed. It was observed that during aging the adrenal gland presents hypertrophy of the fasciculata and reticularis zones. Lipofuscin accumulation was observed during aging, in addition to changes in proliferation, cell death, and cell receptors. The analyses also showed that the gerbil presents steroidogenic enzymes and the production of steroid hormones, such as DHEA, like that found in humans. The data provide the first comprehensive assessment of the morphophysiology of the Mongolian gerbil adrenal cortex during aging, indicating that this species is a possible experimental model for studies of the adrenal gland and aging.

Impairment of steroidogenesis and follicle development after bisphenol A exposure during pregnancy and lactation in the ovaries of Mongolian gerbils aged females.

The ovaries regulate fertility and hormonal control in females, and aging is a crucial factor in this process, when ovarian function is drastically impacted. Exogenous endocrine disruptors may accelerate this process, acting as the main agents in decreased female fertility and hormonal imbalance, since they impact different features related to reproduction. In the present study, we demonstrate the implications of exposure of adult mothers to the endocrine disruptor bisphenol A (BPA) during pregnancy and lactation on their ovarian function during the transition to later in life (aging). The follicle population of BPA exposed ovaries showed impairment in the development of follicles to the mature stages, with growing follicles being halted in the early stages. Atretic and early-atretic follicles were also enhanced. Expression of estrogen and androgen receptors in the follicle population demonstrated impairment in signaling function: ERß was highly expressed in follicles from BPA exposed females, which also showed a higher incidence of early atresia of developed follicles. ERß1 wild-type isoform was also enhanced in BPA-exposed ovaries, compared to its variant isoforms. In addition, steroidogenesis was targeted by BPA exposure: aromatase and 17-ß-HSD were reduced, whereas 5-α reductase was enhanced. This modulation was reflected in serum levels of estradiol and testosterone, which decreased in BPA-exposed females. Imbalances in steroidogenesis impair the development of follicles and play an important role in follicular atresia. Our study demonstrated that BPA exposure in two windows of susceptibility - gestation and lactation - had implications during aging, enhancing perimenopausal and infertile features.

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.