DIFFERENTIAL REGULATION OF HEPARIN-BINDING EPIDERMAL GROWTH FACTOR-LIKE GROWTH-FACTOR IN THE ADULT OVARIECTOMIZED MOUSE UTERUS BY PROGESTERONE AND ESTROGEN

Expression of heparin-binding epidermal growth factor-like growth fact or (HB-EGF) was studied in the adult ovariectomized mouse uterus in re sponse to progesterone (P-4) and/or 17 beta-estradiol (E(2)) using Nor thern blotting, in situ hybridization, and immunohistochemistry. A 2.5 -kilobase transcript of HB-EGF messenger RNA (mRNA) was detected in to tal uterine RNA samples. Although low levels of this mRNA were detecte d in uterine samples of oil-treated ovariectomized mice (control), an injection of E(2) promptly up-regulated the levels. The mRNA levels pe aked at 2 h and returned to basal levels after 12 h. Injection of P-4 alone did not influence the basal levels; however, coinjection of E(2) with P-4 caused a rapid, but transient, up-regulation of the mRNA. Th e levels peaked between 2-4 h and declined 6 h after the hormone injec tions. Coinjection of E(2) with P-4 after 1 day of P-4 priming also re sulted in peak levels of HB-EGF mRNA at 2 h; however, the levels were not sustained thereafter. Because P-4 and E(2) differentially regulate heterogeneous uterine cell types, in situ hybridization was performed to determine cell-specific expression of HB-EGF mRNA in the ovariecto mized uterus before and after steroid treatments. In the oil-treated u terine sections, very low levels of autoradiographic signals were obse rved in the luminal epithelium. In contrast, an injection of E(2) resu lted in a marked accumulation of HB-EGF mRNA primarily in uterine epit helial cells within 2 h. Although specific hybridization signals could not be detected in any uterine cell types after P-4 treatment, combin ed treatment with P-4 and E(2) resulted in an accumulation of HB-EGF m RNA in stromal cells. To determine whether uterine HB-EGF mRNA was tra nslated, cellular distribution of HB-EGF protein was investigated by i mmunohistochemistly. In oil-treated uterine sections, an overall weak immunostaining was noted, whereas no staining could be detected in ute rine sections after P-4 treatment. In contrast, positive immunostainin g was noted in epithelial cells after E(2) treatment. Coinjection of P -4 with E(2) caused immunostaining in the stroma. These results are co nsistent with those of in situ hybridization. The present investigatio n establishes that in the adult ovariectomized mouse uterus, E(2) regu lates HB-EGF expression in the epithelium, whereas expression of HB-EG F in the stroma is regulated by P-4 and E(2).