L-arginine supplementation attenuates capillary regression without increasing integrated succinate dehydrogenase...

Decreased capillary number is observed in atrophied muscle. The change in capillary number is regulated by angiogenic factors. L-arginine enhances expression of endothelial nitric oxide synthase (eNOS), angiogenic factor, in skeletal muscle. Therefore, the aim of this study was to evaluate the effects of L-arginine supplementation on capillary regression during hindlimb unloading. Twenty-four male Wistar rats were divided into four treatment groups: (1) control, (2) L-arginine supplementation, (3) hindlimb unloading, and (4) hindlimb unloading with L-arginine supplementation. Hindlimb unloading resulted in a decrease of capillary-to-muscle fibre (C/F) ratio, eNOS expression, and integrated succinate dehydrogenase (SDH) activity. L-arginine supplementation attenuated the decrease in both eNOS expression and C/F ratio, although it did not increase integrated SDH activity in skeletal muscle. These results indicate that L-arginine supplementation is effective for maintaining capillary number in atrophied muscle, and that elevation of eNOS expression may be one mechanism associated with these responses.