Effects of estrogens in environmentally relevant concentrations on kiss2 and kiss2rb expression in pejerrey fish brain, pituitary and testes.

TOVAR, M.O.; GARRIZ, A.; MENENDEZ HELMAN R. J.; DEL FRESNO, P.; MIRANDA, L.; SOMOZA, G.M.

Buenos Aires

Encuentro; SETAC Latin America 11th Biennial Meeting; 2015

SETAC Latin America

Environmental estrogenic compounds can interfere with the endocrine system and adverse developmental and reproductive effects in animals. Estradiol (E2) and 17α-ethynylestradiol (EE2) contribute to the estrogenic activity in water bodies all over the world. During the last years, a more inclusive concept has emerged: neuroendocrine disruption, in order to include the full breadth of integrative physiology. So, we aimed to study the neuropeptide kisspeptin (kiss), known to control reproductive function in vertebrates. For example, in Danio rerio and Carassius auratus kisspeptin mRNA expression in the brain is increased after E2 treatments and putative binding sites for estrogen receptors (ERs) have been characterized in kisspeptin and kisspeptin (kissr) receptor promoter regions. In most teleost species, the kisspeptin system is composed by two ligands (kiss1 and kiss2) and two receptors (kiss2rb and kiss3rb); and it is known that kiss2/kiss2rb are related to gonadal maturation. In this context, the main of the present study was to evaluate the effects of E2, EE2 and their mixture on kiss2/kiss2rb mRNA expression in the Brain-Pituitary-Testicular axis of pejerrey. To accomplish this goal, five adult males were maintained in 60 L tanks during 14 days, using a static exposure system (by duplicates). Fish were exposed to 350 ng/L of E2 and 45 ng/L of EE2, and the mixture of both estrogens at the same concentrations, and the steroids were added every two days in order to keep their concentration constant. At the end of the exposure, fish were anesthetized and sacrificed. A brain section (from the optic tectum to the inferior lobe of the hypothalamus), the pituitary gland and the testes were dissected, total RNA obtained and cDNA was synthetized by reverse transcription reaction. Kiss2 and kiss2rb expression was measured by RT-qPCR, using ß-actin and elongation factor 1 as reference genes. The estrogens mixture induced a rise of kiss2 and kiss2rb mRNA expression in the brain, compared to the other treatments. No significant differences in kiss2 or kiss2rb levels were observed in the pituitary gland and testes. These results suggest that estrogenic compounds have a differential action on kiss2/kiss2rb expression depending on the tissue and show, that kisspeptin is a target of endocrine disruption. Further studies must be done to clarify this action, probably mediated by ER response elements in pejerrey as it has already been reported for other teleost.