Immunohistochemical localization of NNOS, PRMT and DDAH in the rat central nervous system

Abstract

Nitric oxide (NO) is an important signaling and effector molecule involved in pathophysiological and physiological processes such as neurotransmission. Nitric oxide (NO) is generated from l -arginine by NO synthase (NOS), which has three isozymes: endothelial, inducible and neuronal (eNOS, iNOS and nNOS, respectively) NOSs. One of the l -arginine metabolites N G , N G -dimethylarginine (asymmetric dimethylarginine: ADMA) is a potent inhibitor of nNOS. ADMA is synthesized by protein arginine methyltransferase (PRMT) and is catabolized by dimethylarginine dimethylaminohydrolase (DDAH). In this report we demonstrated the presence and histochemical localization of nNOS, PRMT1 and DDAH1 in the rat central nervous system. Western blot analyses showed that PRMT1 and DDAH1 were widely distributed and the expression patterns were different among the enzymes in the rat central nervous system. The immunohitochemical analyses using the specific antibodies were subjected in the rat spinal cord, cortex, hippocampus, thalamus, and hypothalamus. In the spinal cord, nNOS immunoreactivities were observed in some neurons in dorsal horn and surrounding central canal, and colocalized with PRMT1. PRMT1 and DDAH 1 were colocalized in the neuronal somata. In the cortex and hypothalamus, almost all nNOS neurons had PRMT1 and DDAH1. These findings suggest that PRMT1 and DDAH1 regulate NO/NOS system in the rat spinal cord, cortex and hypothalamus.