Association of heat shock protein 70 with motility of frozen-thawed sperm in bulls

Heat shock protein 70 (HSP70) is considered as a gene which affects semen quality traits. The present study attempted to investigate the relationship between the HSP70 expression level and motility of bull sperm during the process of freezing-thawing. Semen samples were collected from 5 QinChuan bulls by artificial vagina. Sperm motility and plasma membrane integrity of the semen samples at three stages (fresh, after equilibration, and frozen-thawed) were evaluated. The HSP70 expression level at the three stages was detected using real-time PCR. The results indicated that HSP70 expression level, membrane integrity, and sperm motility in the fresh semen were higher than those of the sperm after equilibration and freezing-thawing (P < 0.05), the HSP70 expression level, plasma membrane integrity, and sperm motility in sperm after equilibration were higher than those of the frozen-thawed sperm (P < 0.05). The correlation between HSP70 expression level and sperm motility was positive (ranging from 0.327 to 0.785). The results suggest that HSP70 expression level in bull spermatozoa was gradually decreased following the process of freezing-thawing, and might be associated with bull sperm motility.