Progesterone (P) receptor dynamics in estrogen primed normal human cervix following P injection

Progesterone (P) receptor levels were measured in the cytosol and in the 0.4 M KCl nuclear extract in human cervical tissues with [3H]-R5020 as a ligand and the results compared with those obtained in the myometrium and endometrium of the same uteri. Tissue samples were obtained from 28 women, grouped as follows: group A, 12 premenopausal controls; group B, 7 perimenopausal women who received estrogen 7 to 11 days before operation; and group C, 9 perimenopausal and postmenopausal women who received estrogen as in group B plus P injection 1 to 3 hours before operation. Estrogen administration resulted in a significant rise in total P receptor levels in the cervix, compared with the endometrium and myometrium. P injection after estrogen priming resulted in down-regulation of the P receptor in the cervix to undetectable levels, whereas in the endometrium and myometrium it resulted only in redistribution of the P receptor, with higher nuclear levels and lower cytosol levels. These results indicate the possibility of a different mechanism of regulation of the P receptor in the human cervix, compared with that in the endometrium and myometrium.