Capacitation and acrosome reaction in stallion spermatozoa : functional and clinical aspects

Abstract

Male fertility requires completion of a sequence of elaborate processes including not only spermatogenesis, sperm transport, accessory gland secretion and sperm deposition in the female reproductive tract, but also two very important sperm related events, i.e. capacitation and acrosome reaction. In absence of either no fertilisation in vivo can take place. The site of capacitation in vivo is the oviduct or the uterus, depending on the species, and that of the acrosome reaction is the zona pellucida. A zona pellucida glycoprotein, ZP3 and progesterone are the two most studied physiological inducers of acrosome reaction. Since the report of the presence of progesterone binding sperm proteins, conveniently termed progesterone receptors, on the plasma membrane, progesterone induced sperm acrosome reaction has attracted a great deal of attention.

The work presented in this thesis concerns the membrane changes taking place in stallion spermatozoa during capacitation and acrosome reaction, and the signal transduction mechanism leading to the latter in response to progesterone stimulation. Novel flow cytometry-based techniques for evaluating capacitation and acrosome reaction have been described, and a new parameter to predict male fertility, based on exposure of progesterone receptor, has been proposed.