Effects of in ovo exposure to 17beta-estradiol and bisphenol A (BPA) on the reproductive tract of Caiman latirostris

STOKER C; BELDOMENICO P M; REY F; LUQUE E H; MUÑOZ-DE-TORO M

Buenos Aires Argentina

Congreso; VI Congreso SETAC Latinoamérica; 2003

Exposure to environmental contaminants known as endocrine disruptors (EDs) alters the development and function of reproductive organs in several species. BPA, an ED widely used in the manufacture of polycarbonates, methacrylic and epoxy resins, has been detected in sewage, surface and drinking water, and therefore poses a potentially significant risk for human and wildlife health. Broad-snouted caimans (Caiman latirostris) are widely distributed in northeastern Argentina, and are being used by sustainable ranching programs. Caimans are at the top of the food-web, have a long lifespan and live in aquatic environments. These features make caimans susceptible to EDs exposure. Research on the effects of EDs in these animals is of special interest, not only because caiman populations could be particularly affected, but also due to their potential of being sentinels of ecosystem health by providing sensitive biomarkers of EDs effects. Previously, we showed 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 caiman hatchlings. The aim of the present study was to evaluate the persistence or not of these alterations in juveniles (12 month-old), and also to examine new histomorphological effects on the gonads and external genitalia emerging at this age. Eggs from 5 nests were harvested from areas with very low possibility of contamination and randomly distributed into two incubations groups: 30ºC (female producing temperature) and 33ºC (male producing temperature). All treatments were applied topically to the eggshell at stage 20 of embryonic development. Control eggs received no treatment or vehicle, while treated eggs received either E2 (0.014 or 1.4ppm) or BPA (1.4 or 140ppm). The hatchlings were raised in controlled environmental conditions and food was provided ad libitum until they were sacrificed at the age of 12 months. Serial paraffin-embedded sections of the gonads were stained with trichromic Picrosirius. Seminiferous tubules perimeters were measured on digitalized images using Image Pro-Plus 4.1.0.1® system. A lack of significant disruption of seminiferous tubules histoarchitecture was observed at this age, showing that this is a transient effect observed only perinatally. Polyovular follicles incidence was estimated in five ovary sections from each animal. In one of the five nests, the presence of polyovular follicles was significantly higher in all treated females, except for those treated with the lower dose of BPA (1.4ppm). Interestingly, all the eggs of this nest were substantially larger than the eggs from other clutches, indicating that they were laid by an older female. Phallus tip length and cuff width were measured in digitalized images. Phallus width was significantly lower in females treated with the higher dose of E2, compared with control females. No other differences in phallus size were found. Confirming our previous results, all the eggs treated with E2 1.4ppm or BPA 140ppm incubated at male producing temperature produced females. In conclusion, xenoestrogens effects on C. latirostris reproductive tract were permanent or transient depending on the end point selected.