THE ACROSOME REACTION-INDUCING EFFECT OF HUMAN FOLLICULAR AND OVIDUCTAL FLUID

The human sperm acrosome reaction (AR) can be induced in vitro by a va riety of naturally occurring and synthetic compounds. The present inve stigation determined the effect of human natural cycle periovulatory f ollicular (hFF) and oviductal fluids (hOF) on the human sperm AR in do se-response fashion using the synchronous AR assay. When hFF (30% v/v) or hOF (40% v/v) was added to non-capacitated spermatozoa, no signifi cant (P > 0.05) increase in the % AR was detected in comparison to the non-treatment control. When either of these compounds was added (10%, 20%, and 30% v/v hFF; 20%, 30%, and 40% v/v hOF) to capacitated sperm atozoa (3 hour incubation), a significant (P < 0.05) stimulation of th e AR was detected. Bovine oviductal fluid (bOF) was tested (20%, 30%, and 40% v/v) to determine if it might have an effect similar to hOF. I n contrast to hOF, the highest concentration of bOF (40% v/v) tested f ailed to stimulate a significant (P > 0.05) increase in the % AR of ca pacitated spermatozoa in comparison to control. Inhibitors of protein kinases A (KT5720) and C (calphostin C) were tested to determine their effects on the hFF-induced AR. In comparison to hFF treatment alone, the kinase A inhibitor KT5720 (50 nM, 100 nM) prevented hFF (20%) stim ulation of the AR when added at the end of the capacitation period and 5 minutes prior to the addition of inducer. Similarly, the kinase C i nhibitor calphostin C (50 nM, 100 nM) prevented hFF (20%) stimulation of the AR. The present data demonstrate that periovulatory hFF and hOF stimulate the human sperm AR. hFF appears to stimulate the AR by acti vating multiple signal transduction pathways.