Objective: To evaluate the effects of bisphenol A (BPA) on testosterone levels and sexual behaviors of male mice. Methods: Forty 12-week-old male mice, 22 - 25 g, were randomly allocated into four equal groups (n = 10 per group): the control group and three BPA exposure groups including low concentration group (10 mg/kg), middle concentration group (50 mg/kg) and high concentration group (100 mg/kg). Each mouse received BPA intraperitoneally injected for 21 consecutive days. Sexual behaviors and testosterone levels in serum and interstitial tissue of testis were measured after the last administration of BPA. Furthermore, we also observed the weights of sexual organs of each group, including testis, epididymis and seminal vesicle. Results: The mount latency in the high concentration group, the intromission latency in the middle and the high concentration group were 11.64 ± 2.67 min, 20.28 ± 3.40 min and 20.13 ± 2.06 min respectively. All of them were longer than the control group (all P < 0.05). The mount frequency, intromission frequency and copulatory efficacy in the high concentration group were 0.52 ± 0.15 numbers/min, 0.37 ± 0.12 numbers/min and 0.40 ± 0.03, which were all statistically lower than the control group (all P < 0.05). The average testis weights in the low, middle and high concentration group were 0.198 ± 0.032 g, 0.203 ± 0.037g and 0.183 ± 0.032 g, and the relative testis weight in the high concentration group was 0.637 ± 0.106. All of these data were lower than the control group (P < 0.05, P < 0.05, P < 0.01 and P < 0.05, respectively). The epididymis weight and the relative epididymis weight, the weight of seminal vesicle and the relative weight of seminal vesicle were 0.069 ± 0.010 g, 0.242 ± 0.040, 0.219 ± 0.042 g and 0.760 ± 0.143, and all of them were lower than the control group (all P < 0.05). The serum testosterone levels in the high concentration group, the intratesticular testosterone levels in the middle and the high concentration group were 7.88 ± 1.62 ng/ml, 75.5 ± 7.18 ng/g and 73.00 ± 9.57 ng/g, which were all lower than the control group (all P < 0.05). Conclusions: BPA can decline the testosterone levels in mice and inhibit their sexual behaviors.
Bisphenol A (BPA, chemical structure: C15H16O2) is thought to be an environmental estrogen which generally exists in the environment [
Animals and experiment protocols in the present study were approved by the Sun Yat-sen University Institutional Animal Care and Use Committee. All animals received humane care, and all efforts were taken to minimize suffering. After the experiments, animals received euthanasia by CO2 inhalation.
Forty male C57BL/6 mice and 10 female C57BL/6 mice were purchased from the Animal Center of Sun Yat‑sen University (Guangzhou, China) and were maintained on a 12 h-day/12 h-night schedule (lights on from 19:00 to 07:00 h) at constant temperature (22˚C ± 1˚C) and humidity (60%). These animals were approximately 12 weeks of age and weighted 22 g - 25 g.
BPA and olive oil were purchased from Sigma.BPA was dissolved in olive oil before administration. All of the male mice were assigned into four equal groups (10 male mice per group). One group was treated with physiological saline intraperitoneally as the con- trol group, and the other three groups were treated with BPA via intraperitoneal injection at different dosages for 21 consecutive days (10, 50, 100 mg/kg per day respectively).
As depicted previously, the female mice were used as stimulus females in the test and were resected with double ovaries in advance [
Sexual behaviors tests have been described previously [
After the examination of sexual behaviors, each of the male mice was weighed. Then, all of the animals were anesthetized with ether, and blood samples were obtained from the vena cava for the examination of serum testosterone. Immediately after blood sampled, bilateral testes, epididymides, and seminal vesicles were obtained and weighed.
Serum testosterone was assayed by the enzyme-linked immunosorbent assay (ELISA) kit (R & D Systems, Minneapolis, MN, USA) following the manufacturer’s instructions. Intratesticular testosterone (ITT) concentrations were examined as previously described [
Results were presented as mean ± s.e.m. In all cases, P < 0.05 was thought to be statistically significant. One-way ANOVA for multiple group comparisons was employed to assess the significance of differences. All analytic results were performed using the Graph Pad Software package (GraphPad Software 6.0, La Jolla, CA, USA).
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0.15 numbers/min vs. 0.67 ± 0.13 numbers/min P < 0.05). Similarly, there was a decrease of intromission frequency and copulatory efficacy in the 100 mg/kg group compared with the control group (intromission frequency: 0.37 ± 0.12 numbers/min vs. 0.53 ± 0.17 numbers/min; copulatory efficacy: 0.40 ± 0.03 vs. 0.45 ± 0.02; both P < 0.05).
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Groups | n | BW (g) | TW (g) | Relative TW | EW(g) | Relative EW | SW (g) | Relative SW |
---|---|---|---|---|---|---|---|---|
Control | 10 | 28.500 ± 2.173 | 0.233 ± 0.025 | 0.882 ± 0.108 | 0.081 ± 0.009 | 0.286 ± 0.038 | 0.267 ± 0.055 | 0.945 ± 0.216 |
10 mg/kg | 10 | 27.500 ± 3.240 | 0.198 ± 0.032* | 0.732 ± 0.161 | 0.076 ± 0.012 | 0.280 ± 0.049 | 0.238 ± 0.046 | 0.877 ± 0.219 |
50 mg/kg | 10 | 27.900 ± 2.424 | 0.203 ± 0.037* | 0.734 ± 0.156 | 0.076 ± 0.011 | 0.275 ± 0.054 | 0.234 ± 0.034 | 0.837 ± 0.090 |
100 mg/kg | 10 | 28.800 ± 2.201 | 0.183 ± 0.032** | 0.637 ± 0.106* | 0.069 ± 0.010* | 0.242 ± 0.040* | 0.219 ± 0.042* | 0.760 ± 0.143* |
Notes: BW: body weight; TW: testis weight; Relative TW: TW/BW × 100; EW: epididymis weight; Relative EW: EW/BW × 100; SW: weight of seminal vesicle; Relative SW: SW/BW × 100; *P < 0.05: statistical significance compared with control group; s.e.m: standard error of mean.
ng/ml, P < 0.05). Similarly, the ITT of the 50 mg/kg group and the 100 mg/kg group was both statistically lower than the control group (the 50 mg/kg group: 75.5 ± 7.18 ng/g; the 100 mg/kg group: 73.00 ± 9.57 ng/g; the control group: 85.10 ± 9.71 ng/g. P < 0.05, and P < 0.01, respectively). No changes were observes in other experimental groups compared with the control.
In the present study, we selected adult male C57BL/6 mice as an animal model to test the effects of BPA on testosterone levels and sexual behaviors of male mice. Our results demonstrated that the administration of BPA could decrease the testosterone synthesis in vivo and suppress sexual functions of male mice.
It was reported that male health has been seriously threatened, and the environmental pollution was thought to be the main reason of this phenomenon [
The present experiment investigated the effects of BPA exposure with different concentrationson the sexual behaviors of adult male mice. As far as we know, this research is the first time this topic was conducted on adult male animal mode. We selected 12‑week‑old male mice as an animal model for examining the effects of BPA on sexual functions and testosterone levels in vivo. In order to investigate whether the administration of BPA can have negative effects on the sexual behaviors of male mice, we tested several relevant items described above. The results indicated that BPA can prolong the latency of mount and intromissionbefore ejaculation, and decrease the frequency of them. No obvious difference of ejaculation latency in BPA-treated groups was seen compared with the control group. Copulatory efficacy was also declined by BPA. Accordingto previous articles, latency of mount and intromission isinversely proportional to sexual motivation, while ejaculation latency, intromission frequency, and copulatory efficacy are indicative of potency [
Previous studies have shown that the synthesis of testosterone is modulated by the HPG axis and is primary tothe maintenance of sexual behaviors [
In addition, the weights of reproductive organs were measured. We found that testis weight and relative testis weight decreased after the treatment of BPA. This phenomenon indicated that the function of testis might have been weakened. The weights and relative weights of epididymis and seminal vesicle also declined after the administration of BPA at the dosage of 100 mg/kg, and this might be attributed to the decrease of testosterone synthesis. These results also indicated that BPA might act in a dose-depen- dent manner.
In conclusion, BPA can supress the sexual behavior of adult male C57BL/6 mice, which might be attributed to the impairment of Leydig cells and the decrease of testosterone levels in vivo. So, reducing BPA in environment is very important to male health.
This work was funded by the Fundmental Research Funds for the Central Universities (16ykpy44).
Zang, Z.J., Ji, S.Y., Xia, T.T. and Huang, S.Z. (2016) Effects of Bisphenol A on Testosterone Levels and Sexual Behaviors of Male Mice. Advances in Sexual Medicine, 6, 41-49. http://dx.doi.org/10.4236/asm.2016.64006