Subpopulations of physiological and ovarian follicular fluid peptide induced apoptotic cells.

Ovarian follicular fluid peptide (OFFP) purified from sheep ovaries enhances apoptotic changes in ovarian granulosa cells of mice. To get an insight into the cell subpopulations responding to OFFP, the heterogeneity of granulosa cells was resolved. Subpopulations of granulosa cells were obtained from ovaries of immature mice treated with PMSG alone and autopsied 48 hr (control) and 72 hr after injection (atretic) and from animals injected OFFP 24 hr after PMSG injection and autopsied 24 hr later (OFFP treated) by separation on discontinuous Percoll gradient. Four fractions were collected and studied for their relative distributions and percent apoptotic cells measured by acridine orange staining. FSH binding to granulosa cell (sedimenting as a major) fraction was studied by radio receptor assay. There is a difference in densities in subpopulations of apoptotic cells induced by OFFP and those generated during the physiological process of atresia. This difference may be a reflection of different granulosa cell subpopulations involved in peptide response or differences in phases as the cells transit from normal to apoptotic phenotype. FSH binding to granulosa cells from OFFP treated animals was significantly less than those from control and atretic group.