DIFFERENTIAL DISTRIBUTION OF PURINE METABOLIZING ENZYMES BETWEEN GLIAAND NEURONS

Previous studies showed that in cultured chick ciliary ganglion neuron s and CNS glia, adenosine can be synthesized by hydrolysis of 5'-AMP a nd that the accumulation of the adenosine degradative products inosine and hypoxanthine was significantly greater in glial than in neuronal cultures. Furthermore, previous immunochemical and histochemical studi es in brain showed that adenosine deaminase and nucleoside phosphoryla se are localized in endothelial and glial cells but are absent in neur ons; however, adenosine deaminase may be found in a few neurons in dis crete brain regions. These results suggested that adenosine degradativ e pathways may be more active in glia. Thus, we have determined if the re is a differential distribution of adenosine deaminase, nucleoside p hosphorylase, and xanthine oxidase enzyme fluxes in glia, comparing pr imary cultures of central and ciliary ganglion neurons and glial cells from chick embryos. Hypoxanthine-guanine phosphoribosyltransferase an d production of adenosine by S-adenosylhomocysteine hydrolase activity were also examined. Our results show that there is a distinct profile of purine metabolizing enzymes for glia and neurons in culture. Both cell types have an S-adenosylhomocysteine hydrolase, but it was more a ctive in neurons than in glia. In contrast, in glia the enzymatic acti vities of xanthine oxidase (443 +/- 61 pmol/min/10(7) cells), nucleosi de phosphorylase (187 +/- 8 pmol/min/10(7) cells), and adenosine deami nase (233 +/- 32 pmol/min/10(7) cells) were more active at least 100, 20, and five times, respectively, than in ciliary ganglion neurons and 100, 100, and nine times, respectively, than in central neurons.