Study On Reproductive Toxicity Of Dimethylformamide On Male Mice

Dimethylformamide (DMF) is an important industrial organic material, an intermediate of pesticide and medicine as well as an excellent dissolvent and absorbent of many kinds of gases. It is widely used in fiber-making, leather-making, dye-making, medicine-making and other industrial production. With the development of modern industry, the requirement for DMF increases year by year, so are the workers who have access to DMF. More and more attention has been paid to the effects of DMF on workers' health. The first report of toxicity and occupational hazard of DMF was from Smyth in 1984, which drew the attention of scientists all over the world. There have been hundreds of accidents of occupational hazard of DMF happened in China since 80's. DMF is a moderate toxicant, people can be exposed to it in many ways, one of which is respiratory tract, a main path in occupational enviroment. Other paths like skin and alimentary tract are also possible for DMF to enter human body. Toxicity of DMF is multiorganic and multisystematic. Studies in the past mostly focused on hepatotoxicity of DMF, few paid attention to its reproductive toxicity, especially the male reproducitve toxicity. The present study is aiming to explore the possible effects of DMF on male reproductive system, and to further discover the possible mechanisms.ObjectiveIn order to discover the effects of DMF on male reproductive system and the possible mechanisms, as well as to provide some scientific evidences for making hygienic standards of DMF and for prevention and treatment of reproductive hazards of DMF, KM male mice were administrated subchronically. Changes of testicle tissue structure were observed, sperm counts were counted, sperm motility, abnormal sperm rate and testicle and epididymis viscera coefficient were calculated, changes of activities of testis enzymes and gonadal hormone levels were detected.Methods40 KM mice, weighted about (25±2)g. were raised. Raising conditions were sunlight 12 hours a day, temperature being (23±2)℃and relative humidity being (50±10)%. After one week raising for adaptation, all were distributed to four groups randomly, with 10 mice each group. Three out of four groups were administrated intragastricly with the dosage of 0, 0.5, 1 and 2g/kg (body weight) DMF every day separately for 30 days in a row. The rest one is as control group. All the mice were weighted at the first day of administration, and then once every three days until being sacrificed at the 30th day of administration. Before their being sacrificed, blood was obtained by pulling out their eyes. The obtained blood was kept for one hour at 20℃, and then centrifuged for 20 minutes at 3000pm/min. The upper layer of the centrifuged blood was separated and stored at -20℃for measuring serum T, LH, FSH levels. Both sides of testicles and epididymises were detached from the bodies and weighted and calculated to get viscera coefficient. Two testicles selected randomly from each group were fixed in neutral formalin solution for pathological exam. Other testicles were stored at -80℃for later measurement of enzyme activities including SDH, LDH, ACP, SOD, and contents of MDA and levels of testis T. The left side epididymises were stored at -20℃for sperm counting and determination of abnormal sperm rate, the right side epididymises were used for determination of sperm motility.Results1. Effects of DMF on body weight, viscera weight and viscera coefficient of male miceCompared with control group, mice in all trial groups show significant decrease in body weight statistically (P<0.05) after the treatment. Weights of testicles and epididymises as well as viscera coefficients of testis decrease correspondingly with the increase of administrating dosage. Compared with control group , 2g/kg group shows statistically significant decrease in testicle weight (P<0.01), epididymis weight (P<0.05) and viscera coefficient of testis (P<0.01).2. Effects of DMF on sperm counting, sperm motility and abnormal sperm rate of male miceWith the increase of administrating dosage, sperm counting and sperm motility show decreasing tendencies, which are dose-effect related. Moreover, compared with control group, sperm counts in 1g/kg group and 2g/kg group decrease statistically at 0.05 level, and sperm motilities of the two decrease statistically at 0.01 level, abnormal sperm rates among all trial groups are of no statistically significant difference (P>0.05).3. Effects of DMF on activity of testis enzyme and content of MDA of male miceWith the increase of administrating dosage, activities of ACP, SOD and contents of MDA in testes show increasing tendencies, while LDH and SDH activities are of the opposite. Compared with control group, ACP activities in all trial groups are significantly higher (P<0.01), so are SOD activities in 1g/kg and 2g/kg groups and MDA contents in 2g/kg group; SDH activities in 1g/kg and 2g/kg groups are significantly lower (P<0.01), the same as LDH activities in all trial groups.4. Effects of DMF on gonadal hormone level in serum and testis of male miceCompared with control group, serum LH levels in all trial groups show no statistical difference (P>0.05). Serum FSH levels in all trial groups are higher than control group, with Ig/kg group and 2g/kg group being statistically significant (P<0.05). T levels of both serum and testis in all trial groups are lower than control group, with 2g/kg group statistically significant (P<0.01).5. Effects of DMF on testicular tissue structure of male micePathological sections of testicular tissue show that convoluted seminiferous tubules of trial groups mice become thin, all kinds of spermatocytes in convoluted seminiferous tubules decrease in number, vacuolus can be observed in cells, some spermatogenic cells are even observed fallen into the lumens. Mature sperms in the tubules decrease in number or even completely disappear. Dilated blood capillaries and pultaceous stroma can be observed.Conclusions 1. Subchronical toxication of DMF causes decrease of testicle and epididymis weight, and viscera coefficient of male mice.2. Subchronical toxication of DMF leads to decrease of sperm count and sperm motility of male mice.3. Subchronical toxication of DMF causes morphological change in testis tissue of male mice.4. Subchronical toxication of DMF affects testis T, serum T and FSH level of male mice significantly.5. Subchronical toxication of DMF affects activity of testis enzymes including ACP, LDH, SDH, SOD, and content of MDA of male mice.6. Changes of LDH, SDH and ACP activities in all trial groups suggest that DMF might affect energy metabolism in testis tissue. Changes of SOD activity and MDA content in all trial groups suggest that DMF might cause lipid peroxidative damage to testis tissue. Changes of gonadal hormones in all trial groups suggest that DMF might interfere with reproductive endocrine system of male mice.