Protective effects of nutritional supplementation with arginine and glutamine on the penis of rats submitted to pelvic radiation

Radiotherapy is widely used to treat pelvic malignancies, but normal tissues near the target tumour are often affected. Our aims were thus to determine whether the structural organization of the rat penis is altered by radiation, and whether supplementation with l-arginine (ARG) or l-glutamine (GLN) would have protective effects against these alterations. Groups of rats were treated with: no intervention (CONTR); pelvic radiation, followed by sacrifice 7 (RAD7) or 15 (RAD15) days later; and pelvic radiation, daily supplementation with ARG or GLN, followed by sacrifice 7 (RAD7+ARG, RAD7+GLN) or 15 (RAD15+ARG, RAD15+GLN) days after radiation. Structural components in the corpus cavernosum (CC), tunica albuginea of the corpus spongiosum (TACS) and urethral epithelium (UE) were analysed using stereological and immunohistochemical methods. The results showed that in the CC, connective tissue was increased by 18% in RAD15 (p<0.04), but this change was partially prevented in RAD15+GLN (p<0.05) and RAD15+ARG (p<0.04). The fibrous matrix of the CC trabeculae stained evenly for collagen type I. In RAD15, the intensity of the labelling was increased, whereas in RAD15+GLN and RAD15+ARG the staining was similar to that of CONTR. No staining changes were seen in the groups that were sacrificed 7days after radiation. Cavernosal elastic fibre content in RAD15 was increased by 61% (p<0.004), and this was prevented in RAD15+ARG (p<0.004) but not in RAD15+GLN. In TACS, the amino acids protected (p<0.02) against the radiation-induced 92% increase in elastic fibre content, but only in RAD15. Cell density in the UE, as well as UE thickness, were reduced by 30% in RAD15 (p<0.004), and there were protective effects of both amino acids. In conclusion, radiation-induced alterations in penile structures tend to be more pronounced 15days after radiation session. Both ARG and GLN have protective effects against these changes, with the former being slightly more effective.