Stimulation of human sperm motility by relaxin.

Relaxin has recently been identified in human seminal plasma (SP). This investigation was undertaken to determine the effect of relaxin on sperm motility. Washed ejaculated human sperm were incubated with or without porcine relaxin. In a series of 37 normal specimens (motility greater than or equal to 60%) relaxin attenuated the decline in grade of forward progression and percentage of motile sperm. Relaxin had a similar effect on a series of 47 subfertile specimens (motility 30% to 40%). Endogenous relaxin may play a role in delaying declines of motility and grade of forward progress in ejaculated sperm.