The presence of beta-adrenoceptors in rat endometrium is dependent on circulating oestrogen

It has been proposed that the change in sensitivity of the uterus to catecholamines during the oestrous cycle may result from changes in beta-adrenoceptor density in the myometrium. In the present work we applied the technique of light-microscopic autoradiography using the radioligand [125I]iodocyanopindolol to study the density and distribution of beta-adrenoceptors in the rat uterus during the normal oestrous cycle, following ovariectomy, and after ovariectomy with oestradiol replacement. We found that beta-adrenoceptor density in the endometrium, but not the myometrium, varied during the oestrous cycle, being highest during pro-oestrous. The endometrium of the ovariectomized rats was devoid of any beta-adrenoceptors, whilst that of the oestradiol-treated rats was very intensely labelled. Following ovariectomy there was an increase in beta-adrenoceptor density in the myometrium, but this was not observed in the animals given oestradiol replacement. It appears that both the presence and density of beta-adrenoceptors in rat endometrium is dependent on circulating oestrogens.