Immunoreactive and estrogen-binding estrogen receptors, and progestin receptor levels in uterine leiomyomata and their parental myometrium

Estrogen receptor (ER) and progestin receptor (PR) levels in the myometria and uterine leiomyomata of forty-four women were studied. A radio-ligand method and an immuno-enzymatic method were used for ER measurement, and only a radio-ligand method was used for PR measurement. The leiomyomata contained significantly more PR and estrogen-binding ER than their parental myometria but not the immunoreactive ER per mg of DNA. Nuclear extracts from the myometria contained a high amount of the estrogen-nonbinding immunoreactive ER; in the leiomyomata, the bulk of this particular ER fraction was extracted with cytosol. Dissimilar distribution patterns of immunoreactive, estrogen-nonbinding ER in leiomyomata and normal myometria suggest that an impaired metabolism of ER may contribute to myoma growth.