Expressão de aromatase, receptores de estrógenos e de andrógenos durante desenvolvimento da gônada de podocnemis expansa

Abstract

Podocnemis expansa, considered the largest freshwater chelonium in South America, presents temperature-dependent sex determination during the thermosensitive period. At this stage, the presence of temperature-influenced hormones triggers the formation of a testicle or ovary in the undifferentiated gonad. Among the hormones present in embryonic development, estrogen is a significant constituent for determining female sex. In this context, high incubation temperature regulates aromatase activity and estrogen production; in contrast, low temperatures cause a reduction in estrogen production and the increase of androgenic hormones. The aim of this study was to analyze the expression of androgen (AR), estrogen (ERα and ERβ) and aromatase steroid receptors by means of immunohistochemistry in different regions of the gonad in the bipotential phases (22 ° -27 °) thermosensitive (25 ° - 42 °) and differentiated (more than 37 days of incubation) of P. expansa, as well microscopic changes during gonadogenesis using light microscopy. It was observed that the ERα and ERβ receptors appear together with some differences in localization in the gonadal tissues according to the progression of the embryonic development and the differentiation between testis and an ovary. These receptors presented a basal level of their expression in the bipotential and differentiation phases, presenting a peak of expression when sex is established, located mainly in the primordial germ cells (CGP) and the spinal cord region in both males and females. Regarding the expression of RA, the markings were observed markedly in the CGP in the ovary, with lower markings in the other regions in the bipotential phase. When the female sex establishes itself the levels of the AR remained basal, with increase in the expression of the medullar region. In addition, aromatase expression was concomitant with increased estrogen expression during differentiation in females in the medullary region and males in the interstitial region. The findings of this study showed that such steroid receptors are distributed in different regions of the gonad, which predicts the involvement of these hormones in the development of the structures that make up this organ. Such findings related to the information of the incubation period allowed to establish possible factors responsible for the determination and differentiation of sex, which provides data that will contribute in the future with the maintenance and conservation of the species in the natural environment.