Elisabetta Baldi, Michaela Luconi, Lorella Bonaccorsi, Csilla Krausz and Gianni Forti.

Dipartimento di Fisiopatologia Clinica, Unita' di Andrologia, Universita' di Firenze, viale Pieraccini 6, I-50139 Firenze, Italy.

Received 05/30/96; Accepted 07/30/96; On-line 08/15/96

In vitro capacitation has allowed determining a number of biochemical events that occur in human spermatozoa. It is not clear whether the same or similar events occur during capacitation that takes place in vivo. However, progesterone and platelet-activating factor, present in the follicular fluid and/or cumulus matrix, could facilitate or prime the acrosome reaction in vivo. The responsiveness of spermatozoa to progesterone might be used as a routine clinical test (172-175). Based on such a test, males can be separated into those with normal or reduced sperm response to progesterone (175). Based on such data, the decision can be made to either perform in vitro fertilization or to resort to a more invasive technique such as intracytoplasmatic sperm injection (ICSI).