Gonadal effects of in ovo exposure to 17B-estradiol and BPA observed in 12 month-old Caiman latirostris

STOKER C, REY F, RODRÍGUEZ H, BELDOMÉNICO P, LUQUE EH, MUÑOZ DE TORO MM

UNLP, La Plata, Buenos Aires

Jornada; XI Jornadas de Jóvenes Investigadores de la Asociación de las Universidades del Grupo Montevideo (A.U.G.M.); 2003

Asociación de las Universidades del Grupo Montevideo

Exposure to environmental contaminants known as endocrine disruptors (EDs) alters the development and function of reproductive organs in several species. Bisphenol A (BPA) widely used in the manufacture of polycarbonates, methacrylic and epoxy resins is an ED. BPA has been found in sewage, surface and drinking water, and therefore poses a potentially significant risk for human and wildlife. Reptiles could act as sentinels of ecosystem health by providing sensitive biomarkers of endocrine disruptor’s effects. We selected Caiman latirostris as an animal model to study endocrine disruption caused by BPA. Previously, we demonstrated that in ovo exposure to BPA causes developmental effects similar to those observed after 17b-estradiol (E2), such as sex reversal and altered gonadal histoarchitecture in hatchlings. The aim of the present study was to determine if the effect of exposure in ovo to E2 and BPA observed in hatchling gonads are still present in 12-month-old caimans and/or whether new histomorphological features emerge at this age. C. latirostris eggs from 5 nests harvested from areas with very low possibility of contamination were randomly distributed in two incubations groups: 30ºC (female producing temperature) and 33ºC (male producing temperature). At each incubation temperature, eggs were divided in six experimental groups. All treatments were applied topically to the eggshell at stage 20 of embryonic development. Control eggs received no treatment or vehicle (50ml ethanol), while treated eggs received either 0.014 or 1.4ppm E2 or 1.4 or 140ppm BPA. Four ten-day old animals from each group were sacrificed for our previous study. Remaining animals were raised in controlled environmental conditions and food was provided ad libitum. These animals were sacrificed at 12 months of age. Gonadal-adrenal-mesonephros complexes were dissected, fixed and processed until embedded in paraffin. Serial sections of the gonads were stained with trichromic Picrosirius solution and counterstained with hematoxylin. The perimeters of seminiferous tubules were defined manually on digitized images and measured using Image Pro-Plus 4.1.0.1® system. Follicles were counted in five ovary sections of each animal. Polyovular follicles incidence was estimated as the percentage of total follicles. In 12 months old C. latirostis previous results regarding sex reversion were confirmed, all caimans incubated at male producing temperature and treated with E2 1.4ppm or BPA 140ppm were females. A lack of significant disruption of seminiferous tubules histoarchitecture was observed at this age showing that this is a transient effect observed only perinatally. The incidence of polyovular follicles was significantly higher in all females produced after sex reversion and in females treated with both doses of E2 or with the higher dose of BPA (140ppm). The lower dose of BPA (1.4ppm) did not affect the incidence of polyovular follicles. The higher incidence of polyovular follicles could result in lower reproductive success later in life as it was observed in alligators from a contaminated lake in USA and in mice treated with DES. Our results show that the effects of xenoestrogens on gonadal histoarchitecture are transient, depend on the dose and on the end point selected