The effects of melatonin supplement on paddlefish (Polyodon spathula) sperm quality and ATP content in sperm during in vitro storage

Abstract

Melatonin (MLT) is a well-known antioxidant and can improve sperm quality during storage in many species. In the present study, the effects of different concentration of MLT (0.1, 0.5, 1 and 5 μM) on paddlefish sperm quality and ATP content in sperm were evaluated during semen storage at 4 °C. Compared with other groups, 0.5 μM MLT supplement in semen could be more effective to improve the plasma membrane integrity, maintain the steady reactive oxygen species (ROS) level and inhibit decrease of mitochondrial membrane potential of the non-activated sperm during whole storage. To the activated sperm, the total motility, progressive motility, beat cross frequency of sperm in semen with 0.5 μM MLT was significant higher (p < .05) than other groups at 30 s after activation. And the motility duration of sperm was also prolonged in semen with 0.5 μM MLT after 24 h storage (p < .05). Furthermore, 0.5 μM MLT in semen could maintain a higher ATP content of sperm before and after sperm activation. Compared with the morphology of the non-activated sperm with 0.5 μM MLT, the head and midpiece of the activated sperm with 0.5 μM MLT displayed deformation in hypotonic condition at 24 h storage. The same morphology changes were also appeared in the non-activated and activated sperm at 0 h storage. In conclusion, 0.5 μM MLT in semen is an optimal concentration to maintain the normal physiological function of paddlefish sperm during storage at 4 °C.