A uterine fluid-mediated sperm-inhibitory system.

Abstract

The report suggests that uterine fluid under certain conditions exerts a sperm inhibitory effect. The addition of rat uterine fluid iodide and hydrogen peroxide to washed spermatozoa suspended in a calcium ion-free Krebs-Ringer phosphate fructose medium pH 6.5 resulted in an inhibition of motility which was complete in 10 min. When the spermatozoa were incubated in medium alone they remained fully motile for 2 hr. Deletion of hydrogen peroxide from the system abolished the sperm-inhibitory effect. Some inhibition of motility was evident on prolonged incubation when either uterine fluid or iodide was deleted. Thiocyanate could substitute for iodide and glucose and glucose oxidase could substitute for hydrogen peroxide giving 94% and 95% inhibition respectively. The uterine fluid could be replaced by a preparation of LPO (lactoperoxidase) or less effectively by MPO (myeoperoxidase). This suggests that its sperm inhibitory effect is due to its perioxidase content. The uterine fluid-iodide-hydrogen peroxide system suspended spermatozoa resulted in a decrease in pyruvate oxidation. Unwashed spermatozoa were unaffected by the system suggesting inhibitors in seminal plasma. This was born out by tests which showed the system was inhibited by catalase and by such low-molecular-weight compounds as azide reduced glutathione cysterine ergothioneine and ascorbic acid. Heat-stable low-molecular-weight inhibitors are found in seminal plasma and to a lesser degree in uterine fluid.