PSA Concentrations in Seminal Plasma

¹ Dept. of Res. and Dev., Hybritech Incorporated, subsidiary of Beckman Instruments, Inc., San Diego, CA 92196,
² The Miami Project to Cure Paralysis, and the Dept. of Urol., Univ. of Miami School of Med., Miami, FL 33136
^a Author for correspondence. Hybritech Incorporated, P.O. Box 269009, San Diego, CA 92196-9006. Fax 619-621-4610.

To the Editor:

Prostate specific antigen (PSA) is an important tumor marker for the detection and monitoring of prostate cancer. PSA is secreted by the prostatic epithelial cells into the lumen of the prostate duct during the formation of seminal plasma. PSA is a 30 kDa serine protease that cleaves biological substrates in seminal fluid, including seminogelin I, seminogelin II, and fibronectin, into small peptides, resulting in increased sperm motility (1)(2)(3)(4). PSA has also been shown to cleave other biological substrates, including insulin-like growth factor-binding protein-3 and laminin, indicating the potential role of PSA in the regulation of various biological functions (5)(6). The cellular expression of PSA is under androgen regulation, and the reduction of androgen function (e.g. by administration of finasteride) has been shown to reduce prostate tissue expression of PSA (7)(8). Nonprostatic sources of PSA have now been documented, including the milk of lactating women, amniotic fluid, and cerebrospinal fluid (9).

We report here the PSA concentrations in seminal plasma collected under tightly controlled conditions from 22 young, healthy men. Such information has not been well defined in previous reports because of variability in the collection and storage conditions of seminal plasma (10)(11).

Samples were obtained with informed consent from 22 normospermic volunteers in the Male Fertility Research Program of The Miami Project to Cure Paralysis at the University of Miami School of Medicine, Miami, Florida. All of the volunteers were in good health with no history of infertility or genitourinary disease. Their mean age was 30.3 ± 1.5 (SE) years (range 19–44 years). The subjects produced specimens by masturbation after at least 3 days of abstinence. Aliquots of the raw semen (0.5 mL each, stored in 1.5 mL Eppendorf tubes) were placed in a -80 °C freezer exactly 15 min after collection. The specimens were stored 2–12 weeks before PSA analysis.

The PSA determination was per-formed using the Hybritech Tan-dem^®-MP PSA assay. Multiple dilutions (n = 4) of each specimen were analyzed, and concentrations were calculated by the multiplication of assay results of diluted samples by the dilution factors. The CVs for the mean concentration of the 4 results was <10% for 20 of the 22 determinations and <20% for all of the determinations.

The range of PSA concentration was 0.39–3 g/L (Fig. 1 ); the mean value was 1.29 g/L with a SD of 0.68 g/L. The median value was 1.17 g/L.

View larger version (15K): [in this window] [in a new window]   Figure 1. The distribution of seminal plasma PSA concentrations from 22 healthy donors.

An appreciation of the wide range (10x) of seminal plasma PSA concentrations in healthy male donor specimens may be useful for studies of the biological roles of PSA and the potential effects of pharmaceutical agents on seminal plasma PSA concentrations.

References

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