In mammalian ovaries, the majority of follicles are lost before ovulation by atresia. This degenerative process is initiated or caused by granulosa cell apoptosis. To reveal the androgen-dependent mechanism of selective follicular atresia, the culture model system for agonism and antagonism of the androgen receptor has been established. We examined the influence of an androgen receptor antagonist, 2-hydroxyflutamide (2-Hf), on the incidence of apoptosis in cultured porcine granulosa cells. They were incubated (6 and 12-h) in the presence of testosterone (T, 10(-7)M), 2-Hf (1.7x10(-4) M) or both T and 2-Hf (T+2-Hf), and then analyzed by flow cytometry with fluorescein labelled annexin V. To better imitate in vivo conditions, the intact porcine follicles (6-8 mm in diameter) have been incubated in an organ culture system with the addition of the same factors. Sections obtained from follicles fixed after culture were stained with hematoxylin and eosin, and the presence of apoptosis-related DNA strand breaks was evaluated by the TUNEL method. Estradiol and progesterone concentrations in the culture media were measured by radioimmunoassays. The addition of T or 2-Hf to the culture media caused an increase in the number of apoptotic granulosa cells, while treatment with T+2-Hf decreased it in both in vitro and organotypic models. Follicles cultured with the addition of T or 2-Hf exhibited morphological changes indicating follicular atresia. Granulosal estradiol secretion was considerably stimulated by T+2-Hf. The highest increase in follicular estradiol secretion was observed after the anti-androgen addition. In both granulosal and follicular cultures, the production of progesterone declined in the presence of T or 2-Hf but increased after their simultaneous addition. In conclusion, androgen receptor antagonist 2-Hf attenuates induction of granulosa cell apoptosis in the presence of a high T level. The nature of this protective mechanism as yet is unknown and requires further research.