Expression of alpha and beta estrogen receptors in the chicken ovary

The role of estrogens in hen reproduction is well established. However, the distribution of estrogen receptors in the chicken ovary is unknown. Therefore, the mRNA expression of a (ER alpha and beta (ER beta) estrogen receptors was examined within the ovaries laying hens. Expression of ERs was determined by RT-PCR analysis. The presence of ER alpha and ER beta mRNAs was found in the ovarian stroma and white, yellowish, small yellow and the largest preovulatory (F3-F1) follicles. ER alpha and ER beta mRNAs were detected in the granulosa and theca layers of the walls of preovulatory follicles. The expression of ER alpha mRNA was markedly higher than ER beta mRNA in all examined ovarian compartments. Within the ovary, the relative expression of both ER mRNAs depends on the follicular diameter and the layer of the follicular wall. The results demonstrate the expression of both ER alpha mRNA and ER beta mRNA in all compartments of the chicken ovary, suggesting, different pathways of estrogen action in the avian ovary. Much higher expression ER alpha mRNA indicates that this form of estrogen receptor is predominant in the chicken ovary. The clarification of ER alpha and ER beta participation in the ovarian functions of the birds necessitates further experiments examining ERs at tile protein level.