Exposure to Lambro river water disrupts spermatogenesis in Xenopus laevis

African clawed toad (Xenopus laevis) has been established as a very suitable model for studying the effects of Endocrine Disrupting Chemicals (EDCs) on reproductive biology. In a previous study we demonstrated severe alterations of testis organization (i.e. reduction of tubule diameter and number of germ cell nests and occurrence of small oocytes) in adult male X. laevis following a four weeks exposure to water from the river Lambro (LAM), a contaminated watercourse from Northern Italy. Data were compared with controls and exposed to ethinylestradiol (EE2), tamoxifen (TAM), methyl-dihydrotestosterone (MDHT) and flutamide (FLU), 10-8 M, as positive controls for (anti)estrogenic and (anti)androgenic activities. In this study, following the same experimental design, our attention was focused on the effects on the spermatogenic process. Germ cell nest profile was analysed in both paraffin and resin embedded testis within ten tubule sections for each specimen, numbered and classified into one of four different categories based on the following germ cell type: spermatogonia B (SPGB), primary spermatocytes (SPCI), secondary spermatocytes (SPCII), spermatids (SPD). The contingency test showed a general decrease of cell nests in LAM, EE2 and FLU exposed males and a general increase of cell nests in MDHT and TAM exposed males. Moreover, LAM exposed males, as well as EE2 and FLU exposed males, showed an increase in the number of SPGB nests and a decrease of SPD nests. A decrease of SPCII and an increase of SPCI nests was observed in 100% and in 44.4% EE2 exposed specimen sections, respectively. A decrease of SPCII and an increase of SPCI nests was observed in about 50% and 90% FLU exposed specimen sections, respectively. Even this last feature was less evident in LAM exposed males, data seem to confirm that Lambro river water is polluted by the concomitant presence of EDCs with mainly estrogenic and anti-androgenic modes of actions