Immunohistochemical study of arginase-1 in the spinal cords of rats with clip compression injury.

The expression of arginases, enzymes that catalyze the hydrolysis of arginine to ornithine and urea, was studied in the inflammatory lesions of spinal cord injury (SCI) in rats. The level of arginase-1 expression in rat spinal cords with clip compression injury was determined by Western blot analysis and immunohistochemistry. Western blot showed that the level of arginase-1 increased in the core lesion of SCI at day 1 post injury and continued to increase through days 4 (p<0.05) and 7 (p<0.01). Immunohistochemical analysis showed that arginase-1 was constitutively expressed in neurons and glial cells in sham control spinal cords. In SCI lesions, arginase-1 was additionally detected in inflammatory cells, particularly in isolectin B4-positive macrophages and reactive astrocytes within the core lesion. These findings suggest that the increased level of arginase-1 in SCI is associated with an increase in macrophages and reactive astrocytes, possibly contributing to the modulation of inflammation during the course of SCI.