Effect of testosterone on binding of insulin-like growth factor-I (IGF-I) and IGF-II in growing antlers of fallow deer (Dama dama).

Testosterone regulation of antler growth may be via the insulin-like growth factors (IGFs). Using histological autoradiography we have measured the specific binding of IGF-I and IGF-II to antler sections during normal growth and during the maturation which follows testosterone treatment of adult fallow deer. In antlers from 20 to 100 days following casting, IGF-I binding was constant within each histological region until 80 days. Between this time and 100 days there was decreased binding to chondrocytes (P < or = 0.01) and increased binding to the reserve mesenchyme/perichondrium (P < or = 0.001). Following testosterone treatment, IGF-I binding declined in dermis (P < or = 0.05), reserve mesenchyme/perichondrium (P < or = 0.05), and chondroblasts (P < or = 0.01). Specific binding of IGF-II showed no change during normal or testosterone-stimulated growth. In conclusion, the regulation of antler maturation by testosterone may include IGF action, probably via the Type 1 IGF receptor.