Regional expression of NO synthase, NAD(P)H oxidase and superoxide dismutase in the rat brain

Nitric oxide (NO) derived from the endothelial NO synthase (eNOS) contributes to regulation of cerebral circulation, whereas that produced by neuronal NOS (nNOS) participates in the regulation of brain function. In particular, NO plays an important role in modulation of sympathetic activity and hence central regulation of arterial pressure. Superoxide derived from NAD(P)H oxidase avidly reacts with and inactivates NO and, thereby, modulates its bioavailability. Calmodulin (CM) is required for activation of NOS and soluble guanylate cyclase (sGC) serves as a NO receptor. Superoxide is dismutated to H2O2 by superoxide dismutase (SOD) and H2O2 is converted to H2O by catalase or glutathione peroxidase (GPX). Given the importance of NO in the regulation of brain perfusion and function, we undertook the present study to determine the relative expressions of immunodetectable nNOS, eNOS, CM, sGC, NAD(P)H oxidase and SOD by Western analysis in different regions of the normal rat brain. nNOS was abundantly expressed in the pons cerebellum and hypothalamus and less so in the cortex and medulla. sGC abundance was highest in the hypothalamus and pons, and lowest in the cerebellum and medulla. eNOS and calmodulin were equally abundant in all regions. NAD(P)H oxide was most abundant in the pons compared to other regions. Cytoplasmic SOD was equally distributed among different regions but catalase and GPX were more abundant in pons, hypothalamus and medulla and less so in the cortex and cerebellum. Thus, the study documented regional distributions of NOS, NAD(P)H oxidase, antioxidant enzymes, sGC and calmodulin which collectively regulate production and biological activities of NO and superoxide, the two important small molecular size signaling molecules.