Bisphenol A: Cause of male infertility

The aim of this study was to evaluate the effect of bisphenol A (BPA), a contaminant of resin-based dental composites and sealants, on the fertility of male adult wistar albino rats. Adult male albino rats of strain weighing approx.150-200gm. were divided into four groups of 10 each. BPA (5, 50 and 100 μg /100gm/bw) was administered orally daily to the rats in the test groups and olive oil to the control group for 90 days. Male fertility was assessed periodically by mating each rat with two untreated females. There were significant reductions in the absolute weights of the testes and disrupted spermatogenesis was observed at 50 and 100μg dose level of BPA whereas at 5 μg dose level did not show any such significant effect. Epididymal epithelium degeneration was observed at 5, 50 and100μg dose level. Cauda sperms were found to be reduced in the 100μg dose treated animals. Reduction in the serum testosterone was also observed in treated animals. Study concludes that bpa affects reproduction with impaired fertility in male rats. Introduction In recent years, scientists have increasingly reported evidences that certain pollutants in the environment plays important roles in contributing causes of fertility problems. A wide range of compounds, including components from pesticides to plastics, from detergents to cosmetics registered as pollutant. Bisphenol A (2, 2-bis (4-hydroxyphenyl) propane) (BPA), is the chemical found in polycarbonate plastics, leaches from plastic containers during normal usage, and detectable amounts can be found in many commercial food products and dental sealant (Goodson et al., 2004; Mountfort et al., 1997). It is reported that 10-20 μg of BPA in canned food is leached from the lacquer lining (Brontons et al., 1995). In the saliva of patients who had been treated with a dental sealant, 20-30 μg of BPA/mL was detected (Olea et al., 1996). The current reference dose [50μg/kg/ day (U.S. EPA 1993)] determined by the U.S. Environmental Protection Agency (EPA) is 1/1000 of the level that exerts the lowest adverse effect (LOAEL; 50 mg/kg/day). It is chronically ingested by humans, 95% of adults and children testes have detectable total urinary BPA (Matsumot et al., 2003; Calafat et al., 2008). BPA has also been measured in maternal serum and ovarian follicular fluid, as well as in fetal plasma and amniotic fluid, indicating passage across the placenta (Schonfelder et al., 2002; Ikezuki et al., 2002). BPA has both estrogenic and anti-androgenic effect (Akingbemi et al., 2004; Lee et al., 2003; Wetherill et al., 2007). Toxicological studies (Richter et al., 2007) have pointed out that rodents exposed to BPA during the prenatal period show a large variety of adverse reproductive outcomes, including decreased epididymal weight and daily sperm production, increased sloughing from seminiferous epithelium (Salian et al., 2009a, 2009b; vom Saal et al., 1998) and increased prostate weight (Nagel et al., 1997). Postnatal exposure disrupt blood testis barrier by this germ cell cannot develop into mature sperm and also increases the activation of caspase-3 which cause germ cell apoptosis (Li et al., 2009). Hence, there is a significant risk of BPA exposure during critical development period that are particularly sensitive to changes in estrogenic environment (Vandenberg et al., 2009). During adult exposure changes in sperm morphology like abnormalities in acrosomal cap, vesicle and deformed nuclei were found in Wistar and Swiss rat at 20μg/kg/day(Chitra, Latchoumycandane, & Mathur, 2003). Recent studies showed that the level of testosterone decrease in rats when exposed to different dose level of BPA (Tohei et al., 2001, Mendiola et al., 2010, Wisniewski et al., 2015). Reviewing to all these studies the present study was planned to determine whether exposure of BPA to different dose level affects testicular spermatogenesis or cause any histological changes in reproductive organs, if so, to identify the mechanisms associated with observed effect. Material and Method Adult male Wistar albino rats (Rattus norvegicus), 3 months old, weighing 150-200 grams, were used in present investigation. The animals were maintained in the Departmental Experimental Facility with light and dark (12h: 12h) schedule in individual polypropylene cage (size 43×27×15cm). Animals were fed with rat pellet diet and water ad libitam. The animals were maintained under perfect veterinary supervision and accordance to the guidelines of CPCSEA (CPCSEA, 2010). Test Chemical Bisphenol A (2, 2-bis (4-hydroxyphenyl) propane) (<99% pure) was purchased from sigma Aldrich. This compound was diluted in olive oil to obtain final concentration of the 5, 50 and 100μg/100gm body weight of the animals respectively. Experimental Design Animals were divided into four groups with ten in each and olive oil was used as vehicle. Group I: Control (vehicle treated) Group II: Oral administration of 5μg BPA/100 g/bw Group III: Oral administration of 50μg BPA/100 g/bw Group IV: Oral administration of 100μg BPA/100 g/bw Doses were given for consecutive 90 days. On 91th day of experiment, animals were sacrificed by overdose of anesthetic ether. Body and reproductive organ weight: The body weights of all animals were measured fortnightly. The weights of all reproductive organs of all animals will be obtained at the time of scarification schedule of each group. Fertility Test: The treated adult males were mated with the normal adult females. Each cage contains one male and two female. Mating was confirmed by visual appearances and presence of spermatozoa in the vaginal smear. Following mating pregnant animals will be allowed to complete the term and pregnancy. Histopathology: A portion of reproductive organs testis, epididymis, were fixed in 4% paraformaldehyde, dehydrated in ethanol, cleared in Xylene and embedded in paraffin wax. Five micron thick sections were stained with haematoxylin and eosin for light microscopic observation.