Progesterone plays an important role in the
reproductive function and follicular development in
mammals. The aim of the present study was to examine
the localization of progesterone receptor alpha (PRA) in
ovary of pseudopregnant rabbit by
immunohistochemical methods. Samples were collected
from 14 h. to 18 days of pseudopregnancy. At the first
stage of pseudopregnancy (14 h.), the rabbit ovary
showed moderate immunostaining of PRA in the
granulosa cells and theca interna cells of preovulatory
follicle and in the stroma cells. At the middle stage of
pseudopregnancy (3-7 days), the rabbit ovary showed
strong immunostaining of PRA in ovarian surface
epithelial cells, follicular cells of the primary follicle,
granulosa cells and theca interna cells of the growing
and antral follicles. Moderate immunoexpression of
PRA were observed in the large lutein cells and
endothelial cells of the corpus haemorrhagicum and
corpus luteum and in the stroma cells. At the end of
pseudopregnancy (18 days) strong PRA reactions were
detected in the small lutein cells of the regressed corpus
luteum. Moderate to strong PRA immuno-expression
were observed in the proliferated theca interna cells of
the atretic antral follicles. The atretic large lutein cells
of the regressed corpus luteum showed negative
immunostaining for PRA. This study showed that the
PRA positive small lutein cells of the regressed corpus
luteum and the PRA positive proliferated theca interna
cells of the atretic antral follicles were transformed into
PRA positive interstitial gland cells. In conclusion, the
present study had described the distribution of PRA in the
ovary of pseudopregnant rabbit, which is not discussed
before in the available literature. It also gives more
information about follicular dynamic, formation and
origin of interstitial glands, mechanism of ovulation,
formation and regression of the corpus luteum.