1,25-DIHYDROXYVITAMIN D-3 REGULATES GAMMA-GLUTAMYL-TRANSPEPTIDASE ACTIVITY IN RAT-BRAIN

gamma-Glutamyl transpeptidase (gamma-GT), primarily described as a kid ney enzyme, is also expressed in several cell types of the central ner vous system (CNS). It is involved in the glutathione cycle and in cyst eine transport. Here we report that the specific activity of this enzy me is transiently increased in the rat brain, following a treatment wi th 1,25-dihydroxyvitamin D-3 (1,25-D-3), the active form of vitamin D. In vitro experiments showed that this positive regulatory effect does not affect endothelial cells of the brain microvessels, but does affe ct pericytes and parenchymal astrocytes. Ch ges in the specific activi ty of gamma-GT were not correlated with any important modification of brain amino acid concentrations. Since gamma-GT is thought to particip ate in the scavenging of reactive oxygen species, these data suggest t hat 1,25-D-3 could be an effector controlling detoxification processes in the brain.