Characterization of Hypothalamic-Pituitary-Adrenal/Interrenal axis in the masculinization by high water temperatures in Medaka.

CASTAÑEDA CORTÉS, D.C.; ESTERMANN, M.; SOMOZA, G.M.; FERNANDINO, J.I.

Okazaki

Conferencia; 22nd Japanese Medaka and Zebrafish Meeting (JMZM).; 2016

National Institute of Basic Biology

Medaka (Oryzias latipes) is a teleost fish with an XX/XY sex determination system. It is well known that exposure to high water temperature (HT) during gonadal sex differentiation can influenced sex-reversed of genotype female into phenotypic males in these specie, but the transducer mechanism between temperature and gonadal differentiation has not been fully described. Recently, it was reported that high levels of cortisol, the major glucocorticoid produced by the interrenal cells in teleosts, are involved in theses process. Corticotropin-releasing hormone (Crh), is known primarily for its central role in regulating neuroendocrine responses to stressors via released from the hypothalamus. In the pituitary, Crh stimulating the secretion of adrenocorticotropic hormone (Acth), which stimulate the synthesis and secretion of cortisol in the interrenal gland. Therefore, Crh is considered as regulator the hypothalamic-pituitary-adrenal/interrenal axis (HPA/I). In this context, we proposed determinate if HPA axis is active during development and is the transducer of masculinization by stress. Initially we characterized the expression of Crh in cells and fibers in the brain and pituitary of larvae exposed to HT (32 ºC) and control temperature (24 ºC) by immunohistochemistry since fertilization to hatching. Furthermore, we identified the Acth positive cell in pituitary. Also, we evaluated the transcript levels of crh and acth in both reared temperatures, funding that the levels of both genes decrease in larvae reared at HT with respect to control temperature treatment, presumably by a negative feedback of cortisol. Our preliminary results provide evidence that Crh could be involved in the masculinization by stress.