Expression of progesterone receptor mRNA in the endometrium during the normal menstrual cycle and in Norplant users

The expression of endometrial progesterone receptor mRNA during the human menstrual cycle and in Norplant users was studied using digoxigenin-labelled ribonucleic probes for in-situ hybridization on 6 microns paraffin embedded endometrial sections. The staining intensity was scored blind semi-quantitatively. Blood ovarian steroid concentrations were measured in Norplant users. All data were analysed by analysis of variance. Glandular progesterone receptor mRNA concentrations were low during the menstrual-to-early proliferative stage but increased during the early-to-mid to late-proliferative stage then declined non-significantly over the secretory stage. No such variation was observed in stromal cells. Progesterone receptor mRNA concentrations were lower in Norplant than controls during early-to-mid to late-proliferative stages (in glandular epithelium and stroma) and during secretory stage (in stroma only). Norplant subjects with amenorrhoea had higher concentrations of stromal progesterone receptor mRNA but lower plasma oestrogen concentrations than subjects with breakthrough bleeding. The pattern of variation in progesterone receptor mRNA concentrations during the normal menstrual cycle resembles the published pattern for the receptor protein. The results demonstrate: (i) a differential sensitivity of glandular and stromal progesterone receptors to steroid regulation; (ii) in contrast to previous findings of an increase in immunoreactive progesterone receptor protein in Norplant endometrium, progesterone receptor mRNA concentrations in these tissues were reduced; and (iii) there was significantly more progesterone receptor mRNA in subjects with amenorrhoea than in those with breakthrough bleeding.