Ovulation in plasminogen-deficient mice

Many different studies suggest that plasmin generated from plasminogen play s a crucial role in the degradation of the follicular wall at the time of o vulation. We have assessed the physiological relevance of plasmin on ovulat ion by studying plasminogen-deficient mice. Ovulation efficiency (mean numb er of ova released per mouse) was determined both in a standardized ovulati on model in which 25-day-old immature mice were injected with finite amount s of gonadotropins to induce ovulation and during physiological ovulation u sing adult normally cycling mice. Our results revealed that the temporal on set of follicular wall rupture (first ova observed in bursa or oviduct) was not delayed in plasminogen-deficient mice during gonadotropin-induced ovul ation. However, there was a trend toward slightly reduced ovulation efficie ncy in the plnsminogen-deficient mice. This reduction was only 13% and not statistically significant (P = 0.084) and may be connected to a delayed mat uration of these mice manifested in reduced body and ovary weights. During physiological ovulation adult plasminogen-deficient mice had normal ovulati on efficiency compared with plasminogen wild-type mice. Taken together our results indicate that under the conditions used in this study plasmin is no t required for efficient follicular rupture or for activation of other prot eases involved in this process. Alternatively, the role of plasmin may be e ffectively compensated for by other mechanisms in the absence of plasmin.