DNase activity in human seminal plasma and follicular fluid and its inhibition by follicular fluid chelating agents

Research question: What is the mechanism by which human follicular fluid inhibits seminal plasma DNase activity? Design: Human genomic DNA was incubated with human follicular fluid and seminal plasma (reaction mixture) under different experimental conditions; increasing volumes of human follicular fluid; proteinase K digested or heat inactivated human follicular fluid; and the addition of Ca2+ or Mg2+ to the reaction mixture. Results: Increasing volume of human follicular fluid resulted in a dose-dependent inhibition of seminal plasma DNase activity. Inhibition was not caused by proteins in the human follicular fluid as digestion with proteinase K or heat inactivation of human follicular fluid failed to abolish its inhibitory effect. Addition of divalent cations resulted in a reversion of the inhibitory effect, providing evidence that human follicular fluid inhibition of seminal plasma DNase activity seems to be mediated by a compound with chelating activity. Furthermore, incubation of genomic DNA with human follicular fluid in the presence of divalent cations served to elicit the existence of DNase activity. Conclusions: Human follicular fluid seems to contain a molecule or molecules with chelating capacity that inhibits DNase activity of both follicular fluid and seminal plasma. Our findings provide new insight to understanding sperm preservation and the physiology of fertilization biology.