Low Molecular Weight Proteins in Human Seminal Plasma Electrophoretical Evidence of their Vesicular Origin

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Abstract
The protein composition of seminal plasma (SP), 2-fractions split ejaculates and expressed prostatic secretions (EPS) from healthy and fertile donors or from infertile patients was analyzed under proteolysis-blocking and denaturing conditions by 5-20% gradient SDS-PAGE [sodium dodecyl sulfate polyacrylamide gel electrophoresis]. EPS protein patterns were strikingly similar, both in protein types and concentrations. The same was true for the SP samples. Co-electrophoresis and comparison of the patterns obtained allowed to identify a medium-sized protein (MW 75-80,000 daltons) and low-MW proteins (MW 10-25,000 daltons) as of vesicular origin. Prostatic and vesicular proteins migrated into differemt zones of the gels, giving rise to an unexpected MW complementarity. A similar finding was obtained by comparing the protein spectra of fluid from vesicular massage (EVS), EPS and SP from a man with moderate asthenozoospermia. Analysis of 9 other EVS samples by the same electrophoretical technique revealed that the majority of them were (sometimes heavily) contaminated by prostatic proteins. SDS-PAGE on gradient gels is helpful in distinguishing and characterizing the proteins secreted by the 2 major male accessory glands. Such a finding has both research and clinical applications.