Uptake and Metabolism of Tritiated Oestradiol and Oestrone by Human Endometrial and Myometrial Tissue in Vitro

Abstract

Human endometrial and myometrial tissues were incubated in vitro with [3H]oestradiol-17\g=b\ and [3H]oestrone to study the uptake and interconversion of these two steroids by the tissues. Endometrial tissue displayed a higher capacity for oestrogen interconversion than myometrial tissue and the oxidation of oestradiol-17\g=b\ to oestrone was favoured, rather than the reverse reaction. A greater degree of oxidation was found in tissue taken from uteri in the secretory phase than in the proliferative phase. A study of the distribution of radiometabolites between 'soluble' and 'particulate' fractions of tissue homogenates showed that a greater proportion of the tissue radioactivity was associated with the 'particulate' fraction in the proliferative phase than in the secretory phase. After incubation of endometrial tissue from the secretory phase with tritiated oestrogens there was evidence of the formation of chloroform-insoluble radiometabolites and some of these were tentatively identified as oestrogen sulphates. In a second experiment, the uptake and metabolism of the same two oestrogens by tissue from leiomyomata uteri (fibroids) and normal myometrial tissue were compared. No significant difference between these tissues was found.The results suggest that the levels of 17\g=b\-hydroxysteroiddehydrogenase in the human uterus may be dependent upon the levels of oestrogens in the blood. The lack of a difference in the treatment of oestrogens by fibroid and normal myometrial tissue suggests that these tissues may have a similar mechanism for the uptake and retention of oestrogens.

A randomized, controlled clinical trial comparing the effects of aromatase inhibitor (letrozole) and gonadotropin-releasing hormone agonist (triptorelin) on uterine leiomyoma volume and hormonal status

“…Receptors for both E and P have been identified in leiomyomata (3). In addition to ovarian E, some investigators have shown that leiomyoma tissues are a source of E. Leiomyoma cells express an E synthetase as well as aromatase and convert circulating androgens to E (4)(5)(6)(7)(8)(9). Estrogen secreted by leiomyomata tissue may reach a sufficient concentration within the local compartment to support its own growth, allowing independence from ovarian E (10).…”

Decreased Induced Retention of the Progesterone Receptor in the Nuclear Extract in Human Uterine Leiomyoma in vivo

“…In addition, the levels of both recep tors followed the same changes throughout the cycle as those in the endometrium and myometrium [3,4,12,[21][22][23][24], Previous measurements of the cytosolic levels of the estradiol and progesteroene re ceptors in relation to the levels of these receptors in the corresponding endometrium and myometrium yielded conflicting results [21,23,25,26], However, the results of recent studies [3,4,27], and the present report indicated that the levels of both recep tors are higher in the LM as compared with the tumor-bearing myometrium.…”

Medical Management of Uterine Fibroids

“…Some studies have shown that leiomyoma tissues are a source of estrogen. Leiomyoma cells express an estrogen synthetase as well as aromatase and convert circulating androgens to estrogen [30,32,33]. Estrogen secreted by leiomyoma tissue may reach a sufficient concentration within the local compartment to support its own growth, allowing independence from ovarian estrogen [34,35].…”