Immunocytochemical demonstration of progesterone and estrogen receptors in feathers and skin of adult hens.
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Clinical evidence indicates that ovarian steroids are involved in the control of moulting in the chicken. This immunocytochemical study investigates if feather papillae and growing feathers are target tissues for ovarian steroids. Progesterone (PR) and estrogen (ER) receptors were demonstrated using monoclonal antibodies in feathers and surrounding skin of laying hens. Both receptor types were present in the nuclei of dermal papillae and in the nuclei of the epidermal germinative layer cells of growing and full-grown feathers. In growing feathers most nuclei of the intermediate layer (ramogenic column, rachis, axial plate) were immunostained, but during the final stages of differentiation into barbules, only estrogen receptors remained prominent. Skin adjacent to feathers showed ER and PR receptors in nuclei of cells from epidermis, muscles and arteries. During egg-laying pause, plasma progesterone levels decrease ten-fold and it is supposed that this results in a much greater endocrine efficiency of the remaining estrogen levels which are only reduced by 50% when egg-laying stops. The moult-inhibiting effect of progesterone in laying hens could be due to its well-established downregulation on estrogen receptors and therefore, on the endocrine effect of ER at cellular level in feather papillae. Such may account for the presence of both receptor types on the same feather cells, as observed in the present study.