Observations on Cyclic Nucleotides in Human Semen

¹ Endocrinology and Reproduction Research Branch and the Developmental Endocrinology Branch, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland

In agreement with earlier studies, we have found that the human seminal plasma yields considerably higher values for cyclic nucleotides when compared with spermatozoa. However, we have also shown that these values vary markedly both between different individuals and in specimens from the same individual at different times. Levels recorded for seminal plasma were 25 to 18,937 nM of cyclic AMP and 0.54 to 3.57 nM of cyclic GMP. These levels were unrelated to those of either fructose (from the seminal vesicles) or zinc and citric acid (from the prostate). We have demonstrated also that in most specimens of seminal plasma the level of cyclic AMP remained stable during a 1-hour incubation at 37 C or during prolonged storage at -40 C. Washed sperm suspensions contained 13.2 to 27.2 pmol cyclic AMP/100 million spermatozoa. Adenylate cyclase activity of human semen was confined to the spermatozoa; it was several times higher in the presence of Mn²⁺ than Mg²⁺ and was unresponsive to sodium fluoride. The latter findings are consistent with enzyme activity derived from a dissociated catalytic component of adenylate cyclase.

     Key words: semen, cyclic AMP, cyclic GMP, adenylate cyclase, fructose, citric acid, zinc

Submitted on December 29, 1980
Revised on March 17, 1981
Accepted on April 16, 1981