INSULIN-LIKE GROWTH-FACTOR-I (IGF-I) AND IGF BINDING-PROTEINS IN SEMINAL PLASMA BEFORE AND AFTER VASECTOMY IN NORMAL MEN

Objective: To examine the levels and origins of insulin-like growth factor I (IGF-I) and insulinlike growth factor binding proteins (IGFBPs) in the human male genital tract. Design: Examining seminal plasma before and 3 months after vasectomy. Subjects: Fifteen men who were candidates for vasectomy were included in the study. Main Outcome Measures: Seminal plasma and serum levels of IGF-I, IGFBP-1, and IGFBP-3 were determined by commercially available assays, furthermore, samples were subjected to Western ligand blotting. Results: Seminal plasma concentrations of IGF-I were significantly lower after vasectomy: 18.0 +/- 2.4 mu g/L (before) and 12.5 +/- 1.2 mu g/L (after). When the total ejaculate content of IGF-I was calculated, the figures were reduced by 50% after vasectomy: 45.64 +/- 7.8 ng (before) and 23.45 +/- 3.8 ng (after). The patterns observed for seminal plasma IGFBP-3 concentrations were 844.9 +/- 59 mu g/L (before) and 816.5 +/- 65 mu g/L (after), When the total ejaculate IGFBP-3 content was calculated there was a 36% reduction after vasectomy: 2,300 +/- 251 ng (before) and 1,474 +/- 217 ng (after). Conclusions: A considerable amount of seminal plasma IGF-I and IGFBP-3 may be of testicular origin. Although the physiological significance of IGF-I and IGFBPs in the male reproductive system still remains uncertain, the demonstration of their presence in the testes add support to a functional role in the regulation of gonadal function.