Immunoreactive relaxin-like substance in human split ejaculates.

Immunoreactive relaxin-like substance concentrations were estimated in whole seminal plasma of normozoospermic patients, in seminal fluid of both fractions of split ejaculates, as well as in the seminal plasma of patients affected by excretory azoospermia of various causes. The relaxin concentration was significantly higher in the first fraction of partitioned ejaculates (P less than 0.001). In cases of azoospermia after vasectomy or after epididymal obstruction, the relaxin levels were similar to the values observed in normozoospermia. Relaxin concentrations, however, were high in cases of congenital agenesis of vasa deferentia and seminal vesicles. Relaxin traced in human male seminal plasma seems thus to have an important extragonadic source, probably localized in the prostate.