SPERM MOTILITY INHIBITOR FROM HUMAN SEMINAL PLASMA - ASSOCIATION WITHSEMEN COAGULUM

Human seminal plasma contains a sperm motility inhibitor (SPMI) origin ating from the seminal vesicles as a 52 kDa precursor form that is rap idly degraded by prostatic proteases after ejaculation. In this study, the distribution of SPMI biological activity and antigens was analyse d in chemically induced, as well as naturally occurring, arrest of sem en liquefaction. SPMI activity was detected exclusively in the coagula ted semen fraction at 2200 +/- 560 IU, whereas total seminal plasma pr oteins separated more evenly between soluble and coagulated components (91 +/- 19 and 65 +/- 18 mg, respectively). An SPMI antiserum recogni zed different forms of SPMI precursors at 52, 38, 35, 33 and 20 kDa in the coagulum while the soluble protein fraction contained only one ma jor immunoreactive band at 15 kDa. High levels of SPMI activity (1500 +/- 180 IU/ml) together with high molecular mass forms of SPMI precurs or and low sperm motility (26%) were detected in semen samples that fa iled to liquefy spontaneously at room temperature. Addition of prostat ic secretions to the non-liquefying samples caused a decrease of SPMI activity (330 +/- 17 IU/ml) and transformed the SPMI precursor into lo w molecular mass forms (14-22 kDa) with a concomitant increase in sper m motility to 49%. The results suggest that SPMI is highly associated with the seminal coagulum components as very active forms that may adv ersely affect sperm motility when not properly processed after ejacula tion.