Decreased induced retention of the progesterone receptor in the nuclear extract in human uterine leiomyoma in vivo

Abstract. Progesterone receptor (RP) levels were measured in the cytosol and in the 0.4 M KCl nuclear extract of human uterine leiomyoma, myometrium and endometrium; the synthetic progestin [³H]-R5020 was used as a ligand. The women were divided into groups A-D as follows: A, 7 women with no treatment; B, 7 women who received progesterone injection 1-3 h before tissue collection; C, 4 women who received conjugated estrogens 7-11 days before tissue collection; D, 5 women who received both conjugated estrogen and progesterone treatments. The following results were demonstrated: (1) Total RP levels in the leiomyoma were significantly higher than the corresponding levels in the myometrium of the same uterus; after estrogen treatment these differences diminished. (2) Leiomyoma challenged with progesterone expressed significantly lower RP levels in their nuclei than did the corresponding endometrium and myometrium. These results indicate the possibility of a defect of RP dynamics in human uterine leiomyoma.