Immunohistochemical study of arginases 1 and 2 in the olfactory bulbs of the Korean roe deer, Capreolus pygargus

Arginases are enzymes of the urea cycle that catalyze the hydrolysis of l-arginine to ornithine and urea. The enzymes are core components of the arginine-ornithine-glutamate-γ-amino butyric acid pathway of the central nervous system. In the present study, we immunohistochemically determined the localization of arginase 1 and 2 in the olfactory bulb (OB) of the roe dear (Capreolus pygargus). Reverse transcription PCR revealed that the mRNAs encoding both arginase 1 and 2 were expressed in the OB. Arginase 1 was localized to olfactory nerve axons, calcitonin gene-related peptide-positive mitral/tufted cells (excitatory neurons), and glutamate acid decarboxylase 65/67-immunopositive periglomerular cells of the main olfactory bulb. The arginase 2 immunoreactivities in the OB tissues were similar to those of arginase 1. Furthermore, both arginases were detected in the accessory olfactory bulb. These findings suggest that both arginase 1 and 2 are potentially associated with excitatory and inhibitory neurotransmitter activities in animal OBs, including those of the roe deer.