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Substance P and beta-endorphin act as possible chemoattractants of mouse sperm.

The effect of beta-endorphin and substance P on mouse sperm motion was examined in an in vitro model. The number of mouse sperm cells migrating to mediuin containing substance P in pharmacological concentrations of 5, 25, and 50 ng/mL were significantly higher than the number migrating to control. This effect was observed after 3 h at a concentration of 5 ng/mL and 1 h at 25 and 50 ng/mL. Demonstrated changes in spermatozoa behavior in the presence of substance P were time and concentration dependent. These effects were interpreted as chemotaxis but not chemokinesis of sperm induced by influence of this tachykinin on membrane receptors. The presence of beta-endorphin in incubation fluid in concentrations of 5, 25, and 50 ng/mL did not cause any visible changes or decrease sperm migration. Substance P contained in follicular fluid played a direct and important role in the process of mammalian fertilization.