There is increasing evidence for an important role of the somatotropic axis in male reproductive function. We investigated the effect of recombinant bovine GH (rbGH) treatment for 21 days on semen characteristics in post-pubertal GH-deficient dwarf (dw/dw) rats. Male dw/dw rats at an age of 75-80 days were divided into two groups (n=10 per group) and injected twice per day with either rbGH (2 mu/g/day) or saline. While the concentration (96.4+/-51.3 x10(6) per mi) and morphology of spermatozoa (spermatozoa with normal morphology 73.5+/-6.3 %) in the dw/dw rat were within the normal range, the motility of spermatozoa was very low (27.5+/-11.7 %), establishing a state of sub-fertility. The rbGH treatment markedly increased (p<0.01) motility of spermatozoa (44.5+/-10.7 %) but did not change the concentration (144+/-80.3 x10(6) per mi) and morphology (spermatozoa with normal morphology 79.5+/-6.0 %). The rbGH treatment also significantly increased the concentration of insulin-like growth factor-I (IGF-I) in blood plasma (control 389.1+/-65 ng/ml, rbGH 813.9 ng/ml, p<0.001) and in seminal vesicle fluid (control 11.3+/-3.0 ng/ml, rbGH 16.1+/-5.4 ng/ml, p<0.05). We conclude that rbGH therapy markedly increases motility of spermatozoa in sub-fertile male GH-deficient dw/dw rats. Thus, GH therapy may offer considerable potential for the treatment of impaired male reproductive performance.
