Systemic administration of insulin-like growth factor I (IGF-I) causes growth of the rat prostate

Purpose: To investigate the effects of insulin-like growth factor I (IGF-I) and epidermal growth factor (EGF) on the rat prostate. In addition, we investigated the effect of ornithine decarboxylase (ODC) inhibition with alpha-diflouromethylornitine (DFMO) on the expected growth of the prostate. Materials and Methods: Eight week old Wistar rats were allocated into groups of eight, receiving systemic treatment for 3 and 7 days with either IGF-I (400 mu g./rat/day) or EGF (30 mu g./rat/day) alone or in combination with DFMO. Results: Systemic treatment with IGF-I for 7 days resulted in a 29% (p <0.01) increase in the mean wet weight of the ventral prostate. The mean weight of the dorsolateral lobe of the prostate increased by 39% (p <0.05), and the seminal vesicle and coagulating gland increased 69% (p <0.05) compared to controls. The ODC-activity in the prostate was significantly increased by IGF-I after 3 days of treatment, and administration of IGF-I concomitantly with DEMO significantly inhibited ODC activity and the weight increase of the prostate. Stereological examination of the prostate in the IGF-I-treated animals showed growth of the epithelial component of the gland. Systemic treatment with EGF did not affect the mean weight of the prostate or the seminal vesicle compared to controls. Conclusion: The results demonstrate that treatment with IGF-I but not EGF for 7 days induces profound growth of the rat prostate and the seminal vesicle, and that the growth is dependent on an intact ODC-activity.