Effect of incubating human sperm at room temperature on capacitation-related events.

OBJECTIVE

To determine the effect of human sperm incubation at room temperature (20 degrees C) upon capacitation-related events.

DESIGN

Prospective study.

SETTING

Basic research laboratory.

PATIENT(S): Semen samples were obtained from normozoospermic volunteers. Human follicular fluid (hFF) was collected from women undergoing assisted reproductive treatment.

INTERVENTION(S): Spermatozoa were incubated for up to 18 hours at 20 degrees C and/or 37 degrees C.

MAIN OUTCOME MEASURE(S): Protein tyrosine phosphorylation patterns, development of hyperactivated motility, and induction of acrosome reaction (AR) in response to hFF.

RESULT(S): Spermatozoa incubated for 18 hours at 20 degrees C showed an array of tyrosine phosphorylated proteins similar to noncapacitated cells. After incubation at 20 degrees C, the percentage of spermatozoa displaying hyperactivated motility and undergoing acrosomal loss in response to hFF was significantly lower when compared with cells kept the same time at 37 degrees C. Conversely, spermatozoa incubated overnight at 37 degrees C could respond to hFF, either at 37 degrees C or 20 degrees C. When preincubation at 20 degrees C was followed by sperm exposure to 37 degrees C, capacitation-related events could be activated. In capacitated cells (16 hours at 37 degrees C), 2-hour incubation at 20 degrees C led to a significant decrease in acrosome reaction inducibility, suggesting sperm decapacitation.

CONCLUSION(S): Human sperm incubation at room temperature does not allow capacitation, although it does not affect hFF-induced acrosome reaction in capacitated cells. The blocking effect is overcome when spermatozoa are exposed to 37 degrees C.