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

Objective: To determine the effect of human sperm incubation at room temperature (20degreesC) 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 20degreesC and/or 37degreesC. 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 20degreesC showed an array of tyrosine phosphorylated proteins similar to noncapacitated cells. After incubation at 20degreesC, 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 37degreesC. Conversely, spermatozoa incubated overnight at 37degreesC could respond to hFF, either at 37C or 20degreesC. When preincubation at 20degreesC was followed by sperm exposure to 37degreesC, capacitation-related events could be activated. In capacitated cells (16 hours at 37degreesC). 2-hour incubation at 20degreesC 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 37degreesC. (Fertil Steril(R) 2002;77:252-9. (C) 2002 by American Society for Reproductive Medicine.).