| In this study,ICR male mice were exposed to heat stress at three differenttemperature(37.30°C,22d;36.32°C,12d and35.78°C,20d) to detect different effects ofheat stress on sperm quality and early embryonic development.and whether melatoninadded with water or injected intraperitoneally alleviated heat stress injury. The test wasdivided into four groups, control group (C group), control and melatonin group (CMgroup), heat stress group (H group), heat stress and melatonin group (HM group). Afterheat stress we recorded body weight、testicular weight, sperm density, vitality, acrosomeintegrity, membrane integrity and observed the morphological changes of the testiculartissue.of each male mice of four groups.We also recorded fertilization rate, cleavage rate,four-cell development rate, eight-cell development rate, morula rate, blastocyst rate andblastocyst cell number and the number of apoptotic.after mating with normal female mice.In the first test, the maximum temperature was37.30°C, heat stress time was22daysand melatonin was added with water,so sperm motility and density of group H wassignificantly decreased compared with group C,and even motility was decreased from46.76%to0.71%. For testicular weight and testicular index between Group C and Group Hdifferences were highly significant (p <0.01), and for body weight there was no difference.In the second test, temperature was decreased from37.30°C to36.32°C and heatstress time was reduced from22days to12days Although sperm density, motility andtesticular index were significant between Group C and Group H, the degree of heat stresswas highly decreased. Sperm motility and density of the heat stress group was60.67%and51.31%of the control group.But Melatonin added in the drinking water （0.1mg/ml）alsodidn`t improve sperm density, motility and testicular index.In the third test, temperature of heat stress was decreased from37.30°C to35.78°Cthe maximum temperature was reduced by1.5°C and the heat stress time was basicallysame. After heat stress, sperm density, acrosome integrity, membrane integrity hadsignificant differences compared to the control group and for testicular weight andtesticular index difference was highly significant (p <0.01). In group H seminiferous tubesepithelium was arranged loosely and cell number was significantly reduced, so the spermsgenerated was reduced.There were lots of other changes,such as seminiferous tubulevacuoles. The peritoneal injection of melatonin (10mg/kg.bw.), still had no effect on spermquality and testicular morphology.After male mice in heat stress mating with normalfemale mice, fertilization rate and rate of various stages of early embryonic developmentwere significantly decreased. For the rate of fertilization and embryo development the difference was not still significant,but peritoneal injection of melatonin significantlyimproved rate of fertilization and embryo development. In group HM and group Hfertilization rate were70.15%and61.82%, respectively. Early embryonic developmentfrom cleavage to blastocyst were increased by13.54%,11.43%,11.33%,15.92%,9.33%after adding melatonin.Between heat stress group and control group cell number ofblastocysts had significant differences (54.56vs38.61, p <0.05),and the number ofblastocyst apoptosis had significant differences (6.83%vs11.82%, p <0.05).Between heatstress group and heat stress and melatonin group, for blastocyst cell number and thenumber of apoptotic differences were also significant (38.61vs.49.37, p <0.05and11.82%of vs.5.57%, p <0.05). Melatonin did not improve sperm phenotype, but significantlyimproved sperm DNA damage resluted from the thermal stress,so the rate of fertilizationand embryo development was significantly increased, in particular, blastocyst quality... |
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