NATURAL AND ENDOTOXIN-INDUCED ATRESIA OF PREANTRAL AND EARLY ANTRAL FOLLICLES IS CHARACTERIZED BY DNA INTERNUCLEOSOMAL CLEAVAGE

Preantral follicles (PAF) and early antral follicles (EAF) were isolat ed from bovine ovaries and classified under a stereomicroscope as atre tic or healthy. The atretic follicles were all considered as group I ( in vivo atresia), whereas healthy follicles were assigned to five grou ps (group II, in vivo normal control; group III, in vitro normal contr ol; group IV, in vitro induced atresia; groups V and VI, Lipopolysacch aride (LPS)-induced atresia in vitro). Group I and II follicles were i mmediately snap-frozen (-70 degrees C) until DNA extraction, whereas g roup III-VI follicles were incubated (39 degrees C, 5% CO2, 95% air) f or periods up to 72 hr under various conditions. Group III follicles w ere maintained in complete medium (M199, bovine calf serum, sodium pyr uvate, epidermal growth factor, insulin, transferrin, sodium selenite, penicillin, streptomycin, and amphotericin), whereas group IV follicl es were incubated in the same medium, but without serum. Group V and V I follicles were maintained in complete medium, but in the presence of LPS (10 or 50 mu g/ml, respectively). Results showed that follicles i ncubated in the absence of serum and those exposed to both doses of LP S became atretic. DNA isolated from all atretic follicles showed fragm entation typical of that described for apoptosis; this was also confir med by in situ DNA labeling and histology. Atretic follicles did not p roduce estradiol (P < 0.001), but progesterone values increased with f ollicle size (P < 0.001) and time of incubation (P < 0.001). We conclu ded that in the absence of serum or in the presence of LPS, follicles undergo atresia via apoptosis. (C) 1996 Wiley-Liss, Inc.