| Objective:Heat stress had detrimental effects on the spermatogenesis and sperm quality in boars.But the molecular mechanism has not yet well understood.The previous study on laboratory animals(rat,mouse and monkey)had confirmed that exposure of testes to ambient temperature by experimental cryptorchidism model or local heating causes disruption of spermatogenesis and semen quality.The effect of heat stress on the expression of apoptotic regulating protein Bak and Bclw in boars testis had not been reported.The aim of present study was determine whether or not heat stress had an effect on the apoptotic regulating protein expression of Bclw and Bak in boar testis,thus affect the semen quality.Methods:The present study designed boar testicular heat stress model.Mature boars(Landrace)were used in the study.Parts of the experimental animals were subjected to elevated ambient temperature(37～40℃ for 3 h daily for 7 days)or local heat stress(42℃for 1 h)as experimental group.Other animals were kept in the normal house(20～27℃)as control group.After experiment treatment,all boars were castrated and the testes were harvested.Parts of testis tissue were snap frozen in liquid nitrogen,and then used to extract total protein.Parts of testes tissue were fixed in Bouin’s solution,used to prepare paraffin sections.Western blotting and immunohistochemistry were used to analysis the expression of Bclw and Bak.Result:1 Effect of environmental heat stress on the temperature of scrotum and testis in boarThe infrared themal camera was used to analysis the temperature of scrotum and testis in each group.The results showed that the temperature of scrotum and testis(32.0-34.6℃)is below 3-5℃ than body temperature in normal temperature(20-27℃).When the environmental temperature(37-40℃)is close to or exceed the body temperature,the temperature of scrotum and testis(32.5-37.5℃)will close to the body temperature.2 Effect of environmental heat stress on the semen qualityThe decrease of sperm quality induced by environmental heat stress.Compared with the control group,heat stress increased the sperm abnormality,decreased sperm motility and acrosome integrity.3 Effect of heat stress on the expression of apoptosis regulating proteinWestern blotting showed that the protein expression of Bclw and Bak was all increased significantly in elevated ambient temperature and local heat group as well,compared with the control group.The protein expression of Bclw in elevated ambient temperature group was the highest.And the protein expression of Bak in local heat group was the highest.4 Immunohistochemical showed that Bak and Bclw were co-localized in the cytoplasm of leydig cells,Sertoil cells and all stages of germ cells.Heat treatment resulted in the expression levels of Bclw increased in spermatocytes and posmeiosis germ cells.Heat stress resulted in some spermatogonia,spermatocytes,Sertoli cells and posmeiosis germ cells Bak positive staining increased.Conclusion:The pro-apoptotic protein expression of Bclw and Bak was all increased in response elevated ambient temperature and local heat stress in boar.The results indicated that the expression chang of Bclw and Bak may be associated with the decrease of sperm quality induced by heat stress. |
