Follicular Population and Oestrogen Receptor Alpha in Ovary of the Bitch

The objective of this study was to evaluate the follicular population on ovaries as related to the phases of oestrous cycle and age in bitches. Several characteristics of follicular population on ovaries in follicular (Group 1, n = 3), luteal (Group 2, n = 7) and anoestral (Group 3, n = 8) phases of the oestrous cycle and in young ( ≤ 6 years, n = 12) and old ( ≥ 7 years, n = 6) bitches were observed. The numbers and proportions of primary, secondary, tertiary and atretic follicles, diameters of the follicles and oocytes and distribution of oestrogen receptor alpha in ovaries after ovariectomy were evaluated. Microscopical examination of slices stained with haematoxylin-eosin was performed in 50 mm2 of ovarian tissue in each animal and immunohistochemical detection of oestrogen receptor alpha was performed using a monoclonal oestrogen receptor alpha antibody. Average numbers of all follicles were found 567 (31 % atretic), 449 (27 % atretic) and 408 (37% atretic) in the Group 1, 2 and 3, respectively. Proportions of primary, secondary and tertiary follicles regardless of phase of the oestrous cycle as well as age of animals were 72.0%, 24.5 % and 3.5%, respectively. Proportions of these follicles in various phases of the oestrous cycle as well as in young and old animals were not different. Diameters of primary (40.2 ± 15.20 µm), secondary (102.4 ± 36.60 µm) and tertiary (323.7 ± 95.84 µm) follicles as well as diameters of oocytes i