Protective effects of l-glutamine on the bladder wall of rats submitted to pelvic radiation

Abstract

Radiotherapy is often used to treat prostate tumors, but the normal bladder is usually adversely affected. Using an animal model of pelvic radiation, we investigated whether glutamine nutritional supplementation can prevent radiation-induced damage to the bladder, especially in its more superficial layers. Male rats aged 3–4 months were divided into groups of 8 animals each: controls, which consisted intact animals; radiated-only rats, which were sacrificed 7 (R7) or 15 (R15) days after a radiation session (10Gy aimed at the pelvico-abdominal region); and radiated rats receiving l-glutamine supplementation (0.65g/kg body weight/day), which were sacrificed 7 (RG7) or 15 (RG15) days after the radiation session. Cells and blood vessels in the vesical lamina propria, as well as the urothelium, were then measured using histological methods. The effects of radiation were evaluated by comparing controls vs. either R7 or R15, while a protective effect of glutamine was assessed by comparing R7 vs. RG7 and R15 vs. RG15. The results showed that, in R7, epithelial thickness, epithelial cell density, and cell density in the lamina propria were not significantly affected. However, density of blood vessels in R7 was reduced by 48% (p<0.05) and this alteration was mostly prevented by glutamine (p<0.02). In R15, density of blood vessels in the lamina propria was not significantly modified. However, epithelial thickness was reduced by 25% (p<0.05) in R15, and this effect was prevented by glutamine (p<0.01). In R15, epithelial cell density was increased by 35% (p<0.02), but glutamine did not protect against this radiation-induced increase. Cell density in the lamina propria was likewise unaffected in R15. Density of mast cells in the lamina propria was markedly reduced in R7 and R15. The density was still reduced in RG7, but a higher density in RG15 suggested a glutamine-mediated recovery. Alpha-actin positive cells in the lamina propria formed a suburothelial layer and were identified as myofibroblasts. Thickness of this layer was increased in R7, but was similar to controls in RG7, while changes in R15 and RG15 were less evident. In conclusion, pelvic radiation leads to significant acute and post-acute alterations in the composition and structural features of the vesical lamina propria and epithelium. Most of these changes, however, can be prevented by glutamine nutritional supplementation. These results emphasize, therefore, the potential use of this aminoacid as a radioprotective drug.