GABI DUMITRESCU, IOAN PET, DOREL DRONCA, MIRELA AHMADI, LILIANA PETCULESCU CIOCHINA, NICOLETA MARIOARA FILIMON, ROXANA POPESCU NEW RESEARCH ABOUT THE EFFECT OF OCTYLPHENOL (4-TOP) ON HISTOLOGICAL STRUCTURE OF TESTIS IN MICE The reproductive system of the vertebrates - mainly of the adult males -seems to be vulnerable to the action of endocrine disruptors. The aim of this study was to evaluate the effect of octylphenol (OP) on histological structure of testis in NMRI mice. The mice were divided in three groups (5 mice for each group) such as: control group (C - untreated); vehicle group (V - treated with a mixture of ethanol and corn oil 1:10) and experimental group (E – treated with OP in concentration of 160 mg/kg body weight). The solution of OP was prepared in ethanol, administered by subcutaneous injection in the thigh region (1 ml total volume), for seven consecutive days. For histological examination, after slaughtering, the testes were fixed in 10% neutral formalin, embedded in paraffin, sectioned to a thickness of 5 µm and stained with Mallory’s trichrome method. Microscopic analysis reveals in the individuals from the C and V groups, the normal morphology of the seminiferous tubules. In the case of individuals in the E group, treated with OP, in the testicular parenchyma occurs changes consisting in: detachment of the seminiferous tubule epithelium, mild proliferation of germ cells, the presence of apoptotic bodies among the cells of seminal line, diffuse hyperplasia of the Leydig interstitial cells and hypertrophy of the peritubular capillary. Experimental data obtained in this study demonstrated that the treatment with octylphenol induces irreversible changes in the testicular parenchyma with the disruption of spermatogenesis process.