DIVERSE TESTICULAR RESPONSES TO EXOGENOUS GROWTH-HORMONE AND FOLLICLE-STIMULATING-HORMONE IN PREPUBERTAL BOARS

The effects of exogenous growth hormone (GH) and FSH on development of the testes in intact prepubertal boars was investigated. Twenty-four boars received one of four daily treatments from 8 through 40 days of age: 1) 90 mu g porcine Ip) GH/kg body weight (BW), 2) 100 mu g pFSH/k g BW, 3) GH + FSH, or 4) vehicle only (control). Plasma testosterone l evels, measured at 10-day intervals, were similar among groups of boar s throughout the study. Body weights among groups were similar during treatment, and testicular weight between treatment groups did not diff er at castration (100 days of age). However, total length of the semin iferous tubule per testis in FSH-treated boars was 59% greater than in GH-treated animals (2705 vs. 1704 m; p < 0.05). Diameter of the tubul e in GH-treated boars was 56% greater than in FSH;treated boars (p = 0 .03). Relative mass of spermatocytes and spermatids in GH-treated anim als exceeded that in controls by 2.5-fold and that in FSH boars by 75- fold (p = 0.05). There were no differences in effects of GH + FSH trea tment as compared to control treatment; none of the treatments affecte d any interstitial tissue parameter measured. These results suggest th at exogenous FSH had a mitogenic effect on Sertoli cells while delayin g tubular maturity, whereas exogenous GH promoted tubular and Sertoli cell maturation, defined as increased Sertoli cell size, lumen formati on, and onset of spermatogenesis.