Mechanisms of seminal plasma synthesis and actions on sperm function for advancing reproductive technologies.

Seminal plasma, traditionally regarded as a passive vehicle for sperm transport, is now recognized as a biologically active fluid that is important for normal sperm function and optimal male fertility. This review summarizes how androgen-regulated secretions from the seminal vesicles, prostate, and epididymis influence sperm competence at ejaculation. Key components include seminal vesicle-derived lipids (e.g., oleic acid), prostatic citrate, carbohydrates, ions, and antioxidants that rapidly remodel membranes, activate motility, and preserve genome integrity. Androgen signaling via testosterone and dihydrotestosterone coordinates metabolic programs such as oleic-acid synthesis in the seminal vesicles and citrate secretion in the prostate. Seminal-vesicle fatty acids fuel mitochondrial respiration and support linear motility, whereas prostatic citrate primarily buffers pH and chelates divalent cations that stabilize membranes and acrosomal status. In addition, seminal plasma supplies precursors for cysteine and glutathione biosynthesis, supporting redox homeostasis in sperm. Beyond physiology, timed supplementation with whole seminal plasma or defined components improves motility and fertilization outcomes in livestock and humans. By focusing on how androgen-regulated seminal plasma synthesis influences sperm function, this review outlines mechanisms that are relevant to both male fertility biology and reproductive technologies.