Interleukin 1 beta and GABA-transaminase activity in rat thymus

The occurrence and distribution of 4-aminobutyrate:2 oxoglutarate transamin ase (GABA-t) activity were examined in the rat thymus of normal and immunos timulated rats using biochemical and histoenzymatical methods. Specific GAB A-t reactivity was confined primarily to the arteries and, to a lesser exte nt, to the veins. Only a few activities could be observed in association wi th the subcapsular and medullar part of the parenchyma and nerve fibers. GA BA-t was considered a linking enzyme between the immune and the nervous sys tem and it was studied with the aim of analyzing the relationships between these two systems. Our findings indicate that the GABA-t activity in the th ymus is specifically located in the wall of the blood vessels. Moreover, ou r results demonstrate the presence of a GABA-t activity in the peripheral b lood vessels. Treatment with interleukin 1 beta induces an increase of prot ein content of the amounts of GABA-t biochemically assayed and of the level s of histoenzymatically stained GABA-t. Furthermore, staining of the differ ent structures of the thymus in treated or untreated rats shows that the si gnificant modifications concern the parenchyma, the structures resembling n erve fibers and finally, the whole thymus. On the contrary, the highest act ivity of the GABA-t is located in the walls of arteries, veins and lymphati c vessels. (C) 2000 Published by Elsevier Science Ltd on behalf of Internat ional Society of Immunopharmacology.