Programmed cell death in preovulatory ovine follicles.

Apoptosis is a mode of physiological cell death that occurs during tissue regression and remodeling; it is characterized by macromolecular protein synthesis, oligonucleosomal fragmentation, nuclear condensation, cytoplasmic shrinkage, and dissociation of cell-to-cell junctional complexes. Direct in situ fluorescence detection of digoxigenin end-labeled genomic DNA was used as a marker of nuclear apoptosis within preovulatory ovine follicles and contiguous ovarian tissues. As ovulation approached, there was a progressive increase in apoptotic cells within the ovarian surface epithelium, tunica albuginea, and apical follicular wall. At the avascular site of rupture, follicles were devoid of ovarian surface and granulosa epithelia. Granulosa cell dispersion within the basal region of preovulatory follicles was not associated with apoptosis. Discrete physico-chemical interactions between preovulatory follicles and the ovarian surface are evidently a prelude to programmed cell deletion and ovulation.