Anatomical variation of the oestrogen receptor in normal myometrium

Tissue from 20 surgically resected uteri was examined in order to test the hypothesis that the oestrogen receptor content of the myometrium may not be uniform throughout the uterus. All patients were premenopausal, had no history of any exogenous steroid hormone use and were in the proliferative phase of the menstrual cycle. Material was taken from the subserosal, midmyometrical and subendometrial regions of both the fundal and lower uterine segments. Care was taken to remove all endometrium. Suitable samples were analysed by radioimmunoassay (RIA) for oestrogen receptors. An adjacent block from each area was fixed in formalin and stained immunocytochemically for oestrogen receptors. The results of the RIA show a significantly higher receptor content in the subendometrial region than in either the midmyometrial or the subserosal region. No significant difference was demonstrated between the numbers of receptors in the fundus and in the lower uterine segments. The differences were also well demonstrated by immunocytochemistry, according to which 83% of all cells counted in the subendometrial region were positive, while only 61% of cells in the middle and 47% of those in the subserosal region were positive.