PROTEASES INVOLVED IN FOLLICLE RUPTURE DURING OVULATION

摘要

Ovulation is a dynamic process in which the follicle ruptures and sets free the ovum, enabling it to meet the spermatozoa and become fertilized. The role of proteolytic enzymes in follicle rupture is well recognized. Previously it had been thought that the plasminogen activator (PA)/pIasmin protease cascade played a pivotal role in this process (Tsafriri & Dekel, 1994). However, mice with a deficiency of tissue-type plasminogen activator (tPA), urokinase-type plasminogen activator (uPA), or plasminogen were recently shown to exhibit normal reproduction , indicating that the PA/plasmin system is not essential for ovulation (Carmeliet et al., 1995; Bugge et al., 1995). In spite of these observations, the involvement of this system in ovulation is supported by the results obtained in normal animals in which direct injection of specific antibodies and inhibitors of PA and plasmin into the ovarian bursa caused a significant suppression of ovulation (Reich et al., 1985; Tsafriri et al., 1989) and by more recent studies in mice lacking both tPA and uPA (Leonardsson et al., 1995). To initiate this protease cascade, it is obvious that the activation of PA is necessay.