Effects of Estradiol on Leydig Cell Function and Testicular Development in the Prepubertal Bull

311 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1988.One group (E, n = 5) of beef bull calves was implanted with estradiol-17$\beta$ (E$\sb2$) from birth to 39 weeks of age. A second group (P, n = 5) received placebo. A third (EH, n = 5) and fourth (PH, n = 5) group of bull calves were treated similarly except that they were challenged at 7, 22 and 31 weeks with an intramuscular injection of human chorionic gonadotropin (hCG). Serum hormone levels were determined weekly. At 39 weeks of age, E and P calves were castrated for histologic evaluation of the testes and assessment of in vitro Leydig cell function. Serum E$\sb2$ was greater than 100 pg/ml in all calves at birth but decreased to lower basal levels by day 7 in P and PH. Whereas serum testosterone (T) was observed to rise immediately following birth and remain elevated in P and PH, T did not rise (p $$ 0.1) in basal LH concentration was detected during this period. Serum follicle-stimulating hormone (FSH) was decreased (p $$ 0.1) in vitro. However, exposure to 10$\sp{-6}$ M E$\sb2$ increased T production (p $<$ 0.05).U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD