IMMUNOHISTOCHEMICAL ASSESSMENT OF ESTROGEN-RECEPTOR AND PROGESTERONE-RECEPTOR DISTRIBUTION IN BIOPSY SAMPLES OF THE BOVINE ENDOMETRIUM COLLECTED THROUGHOUT THE ESTROUS-CYCLE

The study was designed to determine the distribution of oestrogen rece ptors (OR) and progesterone receptors (PR) in specific endometrial cel l populations during the oestrous cycle. Uterine biopsy samples and bl ood were obtained from five clinically healthy cows at Days 1 (initiat ion of behavioural oestrus), 8, 15 and 19 of the oestrous cycle. All a nimals conceived after biopsy regimen. Immunoperoxidase staining techn iques at light microscopic level were used to localise OR and PR. Spec ific positive staining reactions for both receptors were always limite d to cell nuclei. Immunoreactivity was scored semiquantitatively. In t he surface epithelium, OR were detectable throughout the oestrous cycl e and exhibited a significant increase from Days 8 to 15. In stromal c ells and glandular epithelial cells, however, staining intensities for OR were strong at behavioural oestrus (Day 1). Significantly lower im munoreactivities were recorded at cycle Day 15. At oestrus, and to a l esser extent at Day 8, a significant gradient in oestrogen receptor co ntent was evident, showing increasing immunoreactivity with the depth of the endometrial tissue. In surface epithelial cells, significantly more progesterone receptor immunoreactivity was evident at Day 8 as co mpared with Days 1, 15 and 19. In glandular epithelia, only some PR st ained at oestrus, many of them occurred at Day 8 and very few could oc casionally be seen at Days 15 and 19. In stromal cells, PR exhibited a somewhat different quantitative staining pattern, i.e. many occurred at Days 1, 8 and 19. A significant decrease in immunoreactivity was ob served between Days 8 and 15. While occasionally recorded smooth muscl e cells of the myometrium could exhibit even strong immunoreactivities for both receptors, such cells of the tunica media of blood vessels w ere almost devoid of OR and PR. Caruncular tissue districts, in a few cases included in biopsy specimens, did not differ substantially from intercaruncular endometrium in OR and PR contents. Endothelial cells, granulocytes and lymphocytes always were devoid of specific nuclear st aining. In the present study, OR and PR contents of the bovine endomet rium exhibit cell type and location specific reaction patterns during the oestrous cycle. This suggests that different cell types ab within this target organ can respond in a different manner to identical hormo nal stimuli.