Abstract
The cell proliferation markers PCNA (Proliferating Cell Nuclear Antigen) and Ki-67 (Proliferating Cell Antigen) were studied in the ovarian follicles and corpora lutea of rabbit ovary during pregnancy. Ki-67 is expressed in the nucleus of the proliferating cells during the active phases of the cell cycle. It cannot be identified in silent or resting cells (Go). In contrast, PCNA expression was homogeneously dense, with nuclei showing variability in staining intensity. Some proportion of cells displaying the immunoreactivity in the cytoplasm as well. The quantity of PCNA-positive cells was higher than that of Ki-67, possibly due to their higher sensitivity. Both antibodies showed similar patterns in the different follicular categories. Granulosa cells of tertiary follicles showed a higher proliferation index. The theca interna presented lower proliferation index when compared with tertiary follicles. In the wall of secondary and tertiary follicles the majority of granulosa and theca cells were positively stained. Express sign of PCNA in granulosa cells begins upon the formation of a primary follicle, and its level of expression appeared to increase during the stages of follicular development. Cells of newly formed corpus luteum were PCNA positive. A higher number of Ki-67 positively stained cells in the CL were much greater in mid-pregnancy than that in late and early pregnancy. Ki-67 staining reached its maximum expression at the late stage of pregnancy. No obvious Ki-67 staining was detected in the early pregnancy. The highest percentage of positive cells was found in granulosa cells of atretic follicles. Tertiary follicles presented higher staining marked cells.