Immunohistochemical Localization of Guanine Aminohydrolase, a Protein Identical with Novel Protein p51-nedasin, and SAP 102 in the Rat Retina / 대한해부학회지

Guanine aminohydrolase (GAH), one of purine metabolizing enzymes rich in the nervous system was proved to have identical amino acid sequence to a recently identified novel protein p51-nedasin, NE-dlg/SAP102-associated protein. Nedasin has been reported to localize at neuronal cell bodies and binds to SAP102, so it might have a role in modulating NMDA receptor 2B clustering of SAP102 or synaptic organization in neuronal cells. In this study, we localize GAH and SAP102 in rat retina using immunohistochemical method. Immunoreactivities are detected for both GAH and SAP102 in ganglion cell layer, inner plexiform layer, inner nuclear layer, outer plexiform layer and pigment layer. They seemed to be colocalized in ganglion cells, amacrine cells, horizontal cells and pigment cells. The staining profile for SAP102 is almost identical with NMDA receptor 2B mainly in fibrous elements in both the inner and outer plexiform layer. Our results support the possibility of close structural relationship between GAH and SAP102 in specific retinal cells and GAH involvement in synaptic organization association with SAP102 in the rat retina.

Localization of Guanine Aminohydrolase in the Postnatl Developing Rat Retina / 대한해부학회지

Guanine aminohydrolase (GAH; Guanine deaminase, EC 3.5.4.3) is an enzyme that has a role in purine catabolism. Most of the enzymes involved in purine catabolism have been studied for their biological functions, physiological roles and amino acid sequences, and biochemical activity of GAH is known to be detected in various organs such as liver, kidney, small intestine and brain. Its activity is also known to be changed during development of the nervous system. Although there have been studies on GAH, the histological distribution of GAH in the rat retina has not been examined until now. In this study, in order to investigate the cellular distribution and temporal regulation of GAH in rat retina, we performed immunohistochemistry in retinal sections at different developmental ages between postnatal day 0 (P0, birthdate) and the adult stage using specific antibody against GAH. GAH immunoreactivity was observed in the ganglion cell layer and inner plexiform layer at P0. From P5, GAH staining appeared in the inner part of the neuroblast layer, where amacrine cells localize. At P14, labeling of GAH also was observed in horizontal cell bodies and in the outer plexiform layer. Immunoreactivity of GAH in horizontal cell bodies was increased and strong punctate reactivity was observed in the outer plexiform layer at the adult rat retina, whereas the number and intensity of immunoreactive amacrine cell bodies in the inner part of inner nuclear layer decreased. From these results, we can suggest that GAH may be involved in the establishment of synaptic connections and signal transduction in the developing rat retina.

Expression of Guanine Deaminase in the Developing Rat Brain / 대한해부학회지

Guanine aminohydrolase (GAH; Guanine deaminase, EC 3.5.4.3) is an enzyme that has a role in purine catabolism. This enzyme produces xanthine and ammonia by hydrolysis of guanine, and xanthine is further degraded to uric acid and hydrogen peroxide by another enzyme, xanthine oxidase. Most of the enzymes involved in purine catabolism have been studied for their biological functions, physiological roles and amino acid sequences, and biochemical activity of GAH is known to be detected in various organs such as liver, kidney, small intestine and brain. Its activity is also known to be changed during brain development. In this study, we hoped to reveal expression pattern of GAH in developing rat brain by western blotting and immunohistochemistry. In western blotting, GAH immunoreactivity was not detected on 14-, 16- and 18-days-old fetal rat brains. Its reactivity was first detected from 20-days-old fetal rat brain and highly increased after birth. And it was maintained at steady level from 2 weeks after birth. In immunohistochemistry, no positive cells were found on 14- and 16-days-old fetal rat brain sections. A few GAH-immunoreactive cells appeared from 18-days-old fetal rat brain and they were localized at olfactory bulb, cerebral cortex, midbrain, pons and medulla. The 20-days-old fetal rat brain also showed immunoreactive cells at hippocampus and the staining intensity was still weak. Postnatal 2-days-old rat brain also showed immunoreactive cells at basal ganglia and the number of positive cells and staining intensity were increased. Thereafter, immunoreactivity appeared on many neuronal cells around various areas in the brain and nerve fibers also showed reactivity on postnatal brains. The number of positive cells decreased from 1 week after birth and a few positive cells were observed on olfactory bulb and cerebellum from 2 weeks after birth. In mature brain most of GAH were localized on nerve fibers and few positive cells could be found on olfatory bulb only. From these, we can suspect that GAH may have some functional relationship with nerve fibers.