Consequences of the treatment with corn oil on the prostate histology and sperm parameters of Mongolian gerbils (Meriones unguiculatus)

A wide range of substances has been used as vehicle in researches with endocrine disrupting chemicals. The main point in the choice of the most adequate vehicle is that it should not influence the results obtained for the compound under investigation. The corn oil, a vehicle widely used in these researches, has phytoestrogens and a high content of linoleic acid in its composition. Due to the fact of some researchers consider this category of fatty acid able to induce inflammatory disorders, it is relevant to evaluate if the corn oil has biological effects and can interfere with the normal development of reproductive organs. Therefore, this study analyzed the effects of treatment with corn oil during gestation on prostate histology and sperm parameters of Mongolian gerbils at adulthood. Male gerbils (n=10 animals/group) were randomly divided into Control (C) and Oil-treated (O – animals treated with 0.1mL of corn oil from 8th to 23rd gestational day, via maternal gavage) groups. Animals (16w old) were weighted, euthanized, the ventral prostatic lobe was fixed in methacarn and processed for paraffin embedding, and testis and epididymis were processed for evaluation of sperm parameters. Testosterone (T) and 17β-Estradiol (E2) analyses were performed by ELISA. Serial prostate sections were stained with Hematoxilin-Eosin (HE) and Gomori’s reticulin, submitted to immunohistochemistry for PCNA and alpha-smooth muscle actin, and the incidence of lesions was evaluated in 25 microscopic sections/group. Stereological analysis of HE-stained histological sections was performed. There was a tendency to reduce the body weight in the O group (C: 70.6±3.3, O: 67.6±3.6g; p=0.0901). The treatment with corn oil during gestation decreased the prostatic weight at adulthood (C: 17.1±4.5; O: 13.3±3.9mg; p=0.0277). Stereological analysis indicated that this reduction was due to a decrease of 32.3% and 24.7%, respectively, in the volume of epithelial and luminal compartments. There was no alteration in the cell proliferation index in the prostate after the treatment with corn oil during the fetal period, but the analysis of lesions incidence indicated the occurrence of reactive hyperplasia in 20% (5/25) of all microscopic sections. The treatment with corn oil during the fetal life did not alter the testis weight (C: 543.2±47.6, O: 519.0±26.3mg; p=0.1616), but there was a tendency to diminish the epididymis weight (C: 203.1±17.5, O: 188.5±12.8mg; p=0.0621). There was no alteration in the daily sperm production; nevertheless, the sperm reserve and sperm transit time in the epididymis diminished in O group. Treatment with corn oil also affected the sperm motility; sperms with progressive movement decreased while those with non-progressive movement enhanced. There was no alteration in the T levels between the groups, but the E2 levels increased 38.6% in O animals. These data indicate that the corn oil treatment during gestation affects the prostatic gland histology, sperm parameters and the levels of circulating estrogen in Mongolian gerbils at adulthood. Taken together, these results are worrying, because they show that the corn oil interfered with the normal development of the reproductive organs, and this fact can result in misinterpretation of the real results of the compound under investigation. (CEUA protocol 93/2014).