Plasminogen activator activity in preovulatory follicles during the ovulatory cycle of the chicken.

The stages of follicular maturation of a preovulatory follicle in the chicken can be divided into an extended proliferative phase (prior to the LH surge) and a brief ovulatory phase (after the LH surge). There is evidence to suggest that plasminogen activator (PA) may play a role in follicular maturation and ovulation in the chicken. The objective of this study was to determine whether PA activity changes in the stigma (site of follicular rupture) and nonstigma regions of the theca layer, granulosa layer, and germinal disc region (germinal disc and adjacent granulosa cells; GDR) during the transition from the proliferative phase to the ovulatory phase and immediately before ovulation. The largest preovulatory follicle (F1) and the second-largest follicle (F2), which would have ovulated first and 26 h later, respectively, were collected at 8 h and 2 h before ovulation (before and after the LH surge, respectively), and at 0.5 h (immediately before ovulation). PA activity in the stigma region of the theca layer in the F1 and F2 follicles was very low at 8 h before ovulation (before the LH surge) and increased dramatically (9-fold) at 2 h before ovulation (after the LH surge). PA activity in the stigma region of the F1 follicles remained high as the follicles prepared to ovulate (0.5 h before ovulation), whereas in the stigma region of the less mature F2 follicles it decreased to a level similar to that measured 8 h before ovulation.(ABSTRACT TRUNCATED AT 250 WORDS)