tokens: Testosterone ( 1 mg . kg ( - 1 ) . d ( - 1 ) , sc ) , the androgen receptor antagonist flutamide ( 10 mg . kg ( - 1 ) . d ( - 1 ) , ip ) , the estrogen receptor antagonist tamoxifen ( 1 mg . kg ( - 1 ) . d ( - 1 ) , ip ) or the aromatase inhibitor letrozole ( 4 mg . kg ( - 1 ) . d ( - 1 ) , ip ) were administered for 6 d after the first injection of STZ .