HUMAN FOLLICULAR-FLUID INHIBITS THE BINDING OF HUMAN SPERMATOZOA TO ZONA-PELLUCIDA IN-VITRO

The effect of human follicular fluid on human zona pellucida binding o f spermatozoa was investigated using the hemizona binding assay (HZA). This effect was compared to that of progesterone, a known component o f human follicular fluid, Exposure of spermatozoa to 25% pooled human follicular fluid for 1 h significantly reduced the number of spermatoz oa bound to zone pellucida when compared to those without human follic ular fluid treatment (149.1 +/- 30.7 versus 177.1 +/- 33.8, P < 0.01), The same phenomenon was observed after 3 h of treatment, The correspo nding numbers of bound spermatozoa were 140.4 +/- 19.1 and 200.2 +/- 2 3.4 (P < 0.0001). Progesterone (1.0 mu g/ml) stimulated the zona pellu cida-binding capacity of spermatozoa significantly under the same cond itions (P < 0.01). The numbers of bound spermatozoa after 1 and 3 h pr ogesterone treatment were 235.5 +/- 44.7 (control, 168.1 +/- 32.9) and 204.3 +/- 27.4 (control, 162.3 +/- 20.1) respectively. HZA comparing the effects of human follicular fluid and progesterone at concentratio ns equivalent to those found in human follicular fluid using matching hemizonae confirmed the inhibitory effect of human follicular fluid on sperm binding to zona pellucida (80.4 +/- 28.4 versus 149.8 +/- 35.2, P < 0.05). This inhibitory effect was also found in another eight ind ividual human follicular fluid samples, Both human follicular fluid an d progesterone did not affect the motility and viability of the treate d spermatozoa when compared to the controls with the same incubation p eriod, Although more spermatozoa underwent the acrosome reaction after 1 and 3 h of human follicular fluid treatment than in the control, th e extent was comparable to those after progesterone treatment. These r esults suggested that human follicular fluid inhibited the zona pelluc ida-binding capacity of spermatozoa in vitro. This inhibitory effect o f human follicular fluid was not mediated by progesterone, and did not result from the effects of human follicular fluid on sperm motility, viability and acrosome reaction.