Preovulatory Collagenase Activity in the Follicle of the Chicken

Abstract

Follicles in the hen ovary are arranged in a hierarchy that allows identification of a preovulatory follicle (F1) that will ovulate next and a less-mature follicle (F2) that will ovulate the next day. Prior to ovulation, collagen fibers are dissociated and/or degraded specifically at the stigma, site of follicular rupture, in both mammals (1, 2) and hens (3). Collagenase activity in preovulatory ovaries increased in PMSG-primed rats following hCG treatment (4, 5). However, it is unknown whether collagenase has a role in ovulation in the hen. Our objective was to determine active and total (active + latent) collagenase activities in the granulosa layer and stigma (S) and nonstigma (NS) regions of the theca layer of Fl and F2 that would have ovulated within ~30 min and 26h, respectively. Collagenase activity was measured using a specific procollagen substrate and is expressed as percent collagen digested ± SE. Collagenase activity was undetectable in granulosa. Active collagenase was greater (P < 0.05) in F1S (18.8 ± 2.1) compared to F1NS (8.8 ± 4.5) and greater (P < 0.01) in the F2S (17.5 ± 4.2) compared to nearly undetectable levels in the F2NS (3.0 ± 2.1). Total activity was greater (P < 0.05) in the theca layer of the F1S (28.0 ± 1.8) compared to F1NS (20.8 ± 1.6) and greater (P < 0.001) in F2S (35.4 ± 2.7) compared to F2NS (14.6 ± 2.2).