Immunohistochemical distribution of oestrogen and progesterone receptors and tissue concentrations of oestrogens in the cervix of non-pregnant cows

Abstract

An immunohistochemical study of the expression of oestrogen (ER) and progesterone receptors (PR) in different regions along the longitudinal and vertical axes of the cervix of non-pregnant cows was performed. Animals were separated into two groups depending on the presence or absence of a functional corpus luteum in their ovaries, as indicated by blood progesterone concentrations. The high progesterone group (HP4) had serum progesterone concentrations >2.0 ng mL^–1 (n  = 6) and the low progesterone group (LP4) had serum progesterone concentrations ≤0.5 ng mL^–1 (n = 4). Significantly higher concentrations of oestrogen were found in the cervical tissue of animals in the LP4 group than those in the HP4 group (473 ± 53 v.149 ± 46 pg g^–1 wet weight; P<0.01). Furthermore, there was a significant effect of tissue layer (epithelium to deep stroma) on the number of ER (P<0.01) and PR (P<0.05) immunoreactive nuclei per 1000 cells. For both ER and PR the proportion of cells expressing the receptor increased from epithelium to subepithelial stroma (P<0.01) and from subepithelium to deep stroma (ER P<0.05; PR P=0.061). When the number of receptor-positive cells were expressed per mm² tissue, differences between the subepithelial stroma and the deep stroma became even more marked. In addition, the vaginal part of the cervix had significantly more (P<0.01) ER and PR immunoreactive nuclei per 1000 cells than the uterine part, but these differences were no longer apparent when a correction was made for cell density. There was no relationship between progesterone status of the animals, nor local tissue oestrogen concentrations and ER or PR immunoreactivity in the cervix of these non-pregnant cows. Instead, a strong relationship between both longitudinal and vertical positioning of tissue in the cervix and expression of both receptor types was shown. In addition, a strong correlation between ER and PR expression in the subepithelial stroma (R = 0.85, P<0.01) and the deep stroma (R = 0.83, P<0.01) was evident. In conclusion, these results demonstrate that in studies of steroid hormone receptor expression in the cervix, careful description of sampling site and depth are necessary if the results are to be interpreted meaningfully.