The Study On Reproductive Toxicity To Underage Male Mice Exposed To Cadmium

Objective To explore the impact of cadmium intoxication on reproductive system and reproductive capability of underage male mice. And enriching the data for the further study on reproductive toxicity of the cadmium.Methods96SPF male NIH mice which were four weeks old were divided into4groups randomly, i.e. the control group, low, middle and high dose groups. There were24animals in each group. Physiological saline and Cadmium Chloride(CdCl2) solution containing β-mercaptoethanol(ME)(the concentration ratio of two components is1:20) were used to inject intraperitoneally into the animals in control group, low, middle, high dose groups at the total dose of0,0.17,0.34,0.68mg Cd/kg respectively. All animals were injected once a day for five days. After the last injection, animals were observed for30,60,90,120days respectively. At each time point,6mice in each group were selected randomly and tested by the following methods:1. Detection for copulating ability:Put female and male mouse into a cage as the ratio of1:1. After the female mouse entered into the cage, time recording began. Writing down the time when male mouse caught the female one the first time as capturing latency of the male mouse. Besides, counting the times of male mouse caughting female one in20minutes.2. Detection for reproductively toxicity of male mice:①Collected the whole blood of each male animal and centrifuged to get the serum for measuring the testesterone(T).②Killed all male mice and brought out their brains, hearts, lungs, livers, spleens, kidneys and testes. Measured weight of these organs, and computed their relative organ weight.③Preserved the whole right kidney, right testis and part of liver separately. By using the Atomic Absorption Spectrometer(AAS), the cadmium contents in each organ was determined.④Separated the right epididymis of each male mice to calculate the sperm malformation rate.⑤Fixed livers, spleens, left kidneys, left testes and left epididymises to check out the pathological changes.3. Detection of copulation rate and conception rate of female mice:Put each male mouse and two female mice into one cage together. The day when vaginal plug was found in female mice was noted as gestational day0(GD0). Every male mouse lived together with the female ones for12days. After that, female mice copulation rate in each group was computed. At GD14, checking out the number of female mice which conceived successfully, then calculating the conception rate of every group.4. Detecting the fetus mouse:Half number of pregnant female mice selected randomly in each group were sacrificed on GD17. Brought out fetus mice, and examined every fetus mouse generally, then, measured the body length, tail length and body weight. Subsequently, fetus mice were dectecd to find out if there were skeletal malformation or visceral malformation.5. Detecting the yong mouse:The other half number of pregnant female mice in each group were allowed to deliver freely. On the21st day after every young mouse were born, they were weighed, meantime, the sex of each young mouse was recorded.6. Calculating the number of live mice(including the fetus mice and young mice) born by each pregnant mouse.Results1. Results for detecting male mice copulating capability:The copulating capability of male mice exposed to cadmium at30,60,90,120d was comparative with that of the control groups.2. Reproductive toxicity of male mice:①T content in serum: Serum T of male animals in middle and high dose group at30d,60d and120d were significantly lower than that of the control(P<0.05). In addition, the serum T of animals in low, middle and high dose groups at90d all showed less than that in the control group(P<0.05).②At120d, the relative organ weight of liver and lung in low dose group, liver relative organ weight in middle dose group were all significantly higher than that of control group(P<0.05).③Cadmium content in organs:Cadmium in livers, right kidneys and testes in low, middle, high dose groups at all time points showed significantly higher than that of control group(P<0.05).④Sperm malformation rate:The sperm malformation rate of mice in low, middle, high dose group were higher than that in control group at30d,60d,90d and120d(P<0.05).⑤Pathological changes in organs: In mice exposed to cadmium, pathological changes occurred in kidneys were mainly phlogocyte infiltration in interstitial tissue, renal tubular epithelial cell degeneration and chronic pyelonephritis. Liver pathological changes mainly includes focal phlogocyte infiltration, extramedullary hematopoiesis, hepatocyte nucleus swelling. Extramedullary hepatopeiesis could also be found in some spleens. Testis pathological changes mainly includes part of limbic seminiferous tubule atrophying, necrosis in testicular tissue. Pathological changes occurred in epididymises were mainly sperm disappearing in duct of epididymises, exfoliated spermatogenic cells appearing in duct of some epididymises.3. The copulating rate and conception rate of female mice:The copulating rate and conception rate of female animals in all cadmium exposure groups were comparative with that of control group.4. Results for fetus mice detection:The body length, tail length and body weight of fetus mice in all cadmium exposure groups were at90d were comparative with that of fetus mice in control group. By skeletal malformation detection, it was found that dysostosis occurred in the phalange and vertebral body of cervical vertebrae in some fetus mice in3.36mg Cd/kg group at120d. Besides, in some cervical vertebrae, ossification center could not be found. None visceral malformation were found in all fetus mice.5. Results of detecting young mice: The body weight of young mice in3.36mg Cd/kg group at120d was significantly lower than that of control young mice. The body weight of mice in other cadmium exposure groups were comparative with that in control groups. The proportion of female young mice to all mice showed no significantly differences among all groups at all time points(P>0.05).6.The number of live mice born by each pregnant mice was comparative(P>0.05) among all groups at30,60,90,120d.Conclusions After male underage mice were exposed to cadmium several times in a short period, when they grew up, the reproductive toxicity may include: androgen content decreasing, sperm malformation rate increasing, pathological changes occuring in testis, epididymis. Additionally, the offsprings of these mice may also be influenced, thus the body and skeleton growing would also be put off.