1,25-dihydroxyvitamin D-3 regulates gamma-glutamyl transpeptidase activity in rat brain

gamma-Glutamyl transpeptidase (gamma-GT), primarily described as a kidney enzyme, is also expressed in several cell types of the central nervous system (CNS). It is involved in the glutathione cycle and in cysteine transport. Here we report that the specific activity of this enzyme is transiently increased in the rat brain, following a treatment with 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 affect pericytes and parenchymal astrocytes. Ch ges in the specific activity of gamma-GT were not correlated with any important modification of brain amino acid concentrations. Since gamma-GT is thought to participate in the scavenging of reactive oxygen species, these data suggest that 1,25-D-3 could be an effector controlling detoxification processes in the brain.