Localization of Plasminogen in the Extracellular Matrix of Hamster Eggs: Exogenous Activation by Streptokinase

JIMÉNEZ-DÍAZ,, MARÍA; ROLDÁN, MARIELA AND MICELI, DORA C.

MOLECULAR REPRODUCTION AND DEVELOPMENT

Wiley-Liss

Lugar: New York; Año: 2002 vol. 61 p. 528 - 535

1040-452X

 The plasminogen activator (PA)/ plasminogen/ plasmin proteolytic system has begun to be taken into account in the fertilization process. In this study we demonstrated the presence of plasminogen in the extracellular matrix (ECM) of hamster oocytes by indirect immunofluorescence and immunoperoxidase assays using human anti-plasminogen. Plasminogen appeared first on the zona pellucida (ZP) of ovarian oocytes and later on the plasma membrane of oviducal eggs. This would suggest that oviducal oocytes modulate the expression of plasminogen binding sites. Plasminogen, known to be activated by streptokinase (SK), is rapidly converted to a plasmin-SK complex. We demonstrated the rapid formation of an SK-plasminogen complex which yields plasmin in the blood plasma of hamsters. Zona Pellucida dissolution time (ZPdt) assays showed that both the in vivo and in vitro SK treatment of eggs from superovulated female hamsters caused an increase in the solubility of the ZP, probably due either to the proteolytic effect of plasmin or to the SK-plasminogen complex. Extracellular proteolysis assays carried out on agar-casein plates confirmed the proteolytic activity of SK-incubated eggs; the controls, on the contrary, failed to display a halo. These studies show that I) superovulated hamster eggs contain plasminogen in their ECM, II) oviducal eggs exhibit plasminogen on their plasma membranes, indicating the presence of their corresponding binding sites, III) in hamsters, SK would be capable of activating ECM plasminogen to plasmin, IV) plasmin is capable of changing the ZPdt with a-chymotrypsin .