Fluorescence spectra from human semen and their relationship with sperm parameters

Fluorescence spectra of human semen, seminal plasma, and spermatozoa were investigated. A total of 51 semen samples were obtained from 45 men, including 40 suspected subfertile men and 5 normal volunteers. Fluorescence spectra excited at 488 nm for each component in 10 mM phosphate-buffered saline (PBS) were scanned in a range of 500 to 700 nm. Under these conditions, emission peaks from each component were observed at 622 nm. The intensity of emission peaks from spermatozoa at 622 nm correlated strongly with the concentration of spermatozoa (r = .837, p = .0001). Sperm motility also correlated significantly with fluorescence intensity emission peaks from spermatozoa (r = .369, p = .019) and semen plasma (r = .356, p = .024). To clarify the origin of emission peak of 622 nm with 488 nm excitation, some components in seminal plasma were dissolved in PBS and the fluorescence spectra were measured. The standard single solutions in PBS, such as citric acid, zinc, calcium, and riboflavin (vitamin B2), did not yield an emission peak of 622 nm with 488 nm excitation. However, blood plasmas and albumin revealed similar fluorescence peaks at 622 nm. Thus, the fluorescence spectra may originate from some protein complex.