PARTIAL CHARACTERIZATION OF THE PLASMINOGEN-ACTIVATOR PRODUCED BY OVINE EMBRYOS IN-VITRO

The type of plasminogen activator (PA) produced by Day 7, 9, and 11 ov ine embryos in vitro was partially characterized. PA activity in the c onditioned medium did not change (p > 0.05) up to equivalent gestation al Day (EGD) 14 but increased to peak levels on EGD 15 (p < 0.05). Zym ographic analysis of conditioned medium and embryos revealed one plasm inogen-dependent lytic zone (48-51 kDa) within EGD 8-15 and a second p lasminogen-dependent lytic zone that appeared after EGD 13 (79-83 kDa) . Addition of the urokinase competitive inhibitor, amiloride, to the z ymograph inhibited plasminogen-dependent lytic activity; and forms of both high and low molecular mass were immunoprecipitated with antiseru m to bovine urokinase-type PA. PA activity in conditioned medium was c ompletely suppressed by amiloride treatment (p < 0.05) but was increas ed (p < 0.05) after incubation with antibodies to human PA inhibitor ( PAI)-2. Treatment with antibodies to human PAI-I did not increase (p > 0.05) PA activity in conditioned medium. These results suggest that D ay 7, 9, and 11 ovine embryos produce a urokinase-type PA (49.9 +/- 0. 5 kDa) and possibly a PAI-2-like protein that associates with the PA a nd forms a PA-PAI complex of high molecular mass (81.4 +/- 1.2 kDa).