Enhancement of sperm motility by bradykinin and kinin analogs

Washed human spermatozoa were incubated with different concentrations of bradykinin, des-arg9-bradykinin, and Ile-Ser-bradykinin (T-kinin). Bradykinin significantly increased the total motility of human spermatozoa at a very low concentration (10(-9) M corresponding to about 1 ng/ml). Enhancement of sperm motility was dependent on the bradykinin concentration, and the effect showed saturation at concentrations above 10(-8) M bradykinin (i.e., sperm motility does not increase further with increasing bradykinin concentration). In the concentration range between 10(-11) to 10(-6) M, des-arg9-bradykinin and T-kinin showed no significant change in motility of washed human spermatozoa. The low effective concentration and the saturation of the effect at higher concentrations of kinin makes it probable that the action of bradykinin is mediated by a specific bradykinin receptor. The kinin receptor of human spermatozoa should be of subtype B2 because the specific B1-agonist, des-arg9-bradykinin, showed no influence on sperm motility.