Y₁R expression in MCF-7 xenografts is down-regulated by antiestrogens in vivo.

<p>Effect of estradiol and tamoxifen on Y₁R expression by MCF-7 (L) xenografts in vivo determined by autoradiography using the selective Y₁R antagonist [³H]-UR-MK114 (3 nM). Subcutaneously grown tumors from NMRI (nu/nu) mice bearing subcutaneous 17β-estradiol depots. The control group (3 mice, C1–C3) was treated with the vehicle (PEG400/1.8% NaCl, 1∶1). Tamoxifen group (3 mice, T1–T3): A cumulative dose of tamoxifen citrate (36 mg/kg, dissolved in PEG400/1.8% NaCl, 1∶1, at a concentration of 2.4 mg/mL) was administered by injecting three times (on day 2, 6 and 10 after explantation of the estrogen depots) 12 mg/kg subcutaneously.