Efeitos de estrógenos ambientais sobre a reprodução do lambari Astyanax rivularis no Alto Rio das Velhas, bacia do Rio São Francisco

Abstract

The Velhas River, an important tributary of the São Francisco river basin, is considered the most polluted river in the state of Minas Gerais, due to the high amount of water contamination from domestic and industrial sewage. The main objectives of this study were to evaluate the effects of environmental estrogens on the reproduction of the species Astyanax rivularis, a small species found in streams with high altitudes in the upper Rio de Velhas and to evaluate the immunostaining of CYP19, ERá and ERâ in the testis along the gonadal development and among sites with different estrogenic contamination. Four field samples were collected in three streams: S1 (low anthropogenic interference) S2 and S3 (contaminated by domestic sewage without treatment). The hepatica expression of a number of molecular (Zrp, Vtg, IGF-I, CYP19, ERá and ERâ) and histological biomarkers (oocytes histopathology and intersex), reproductive endpoints (gonadossomatic, hepatossomatic, Fulton, fecundity and proportion of gametogenic lineage cells) and deviations in the sexual proportion were assessed in the different collection sites. The physicochemical parameters were evaluated by Horiba probe and estrogenic compounds by liquid chromatography coupled to mass spectrometry (LC-MS). Sites exposed to domestic sewage presented high levels of estradiol, estriol, estrone, bisphenol A and nonylphenol when compared to S1. The physical-chemical parameters (temperature and dissolved oxygen) had no differences between the collection sites. The results indicate endocrine disruption in sites exposed to domestic sewage (S2 and S3), such as increase in the proportion of females, increase of Vtg, Zrp, CYP19, ERá and ERâ levels in males and decrease of Vtg in females. Male IGF-I in S2 was low in relation to the reference site. In S2 and S3, a high proportion of yolk deficient oocytes was observed, and in S3 there was an increase in over-ripening oocytes. The proportion of follicular atresia was low and did not present significant differences among the populations of females sampled. The intersex condition was found only in sites exposed to domestic sewage. Morphometric analyzes of gametogenesis demonstrated a higher proportion of vitellogenic oocytes and spermatozoa in S1 than fish captured at sites S2 and S3. The results of immunohistochemistry demonstrated CYP19 labeling in Leydig cells and acidophilic granulocytes, spermatogonia, Sertoli cells, spermatids and spermatozoa. ERá showed a broader distribution than ERâ being found in all stages of germ cell development. On the other hand, ERâ was found only in spermatogonia and spermatocytes. Both ERs were expressed in Leydig and Sertoli cells. During testicular maturation, ELISA levels for CYP19, ERá and ERâ followed the gonadosomatic index (GSI) with significantly higher values at the mature stage. The observed reproductive effects are related to the increase of urbanization and release of domestic sewage directly into water bodies without any treatment and even if the populations of A. rivularis are inhabiting lotic environments and with high water renewal the release of pollutants through sewage is constant, thus promoting chronic exposure of fish to these endocrine disrupters.