| Abstract: | Differences in the distribution of gamma-glutamyl transpeptidase (GGT) activity during early and late postnatal development of the mouse brain were studied at the cellular and regional level. From the 7th to the 25th day of brain development, GGT activity rose evenly in the neuronal perikarya, glial cells and in the neuropil. At 25 days and 5 weeks of age, a 1.5-fold enrichment was observed in nerve cell bodies and in neuroglia as compared with the neuropil and the original cell suspension. During the same period, an abrupt increase in GGT activity was observed in brain capillaries, and between the 10th day and the 5th week, this was 1.5-5 times higher than the enzyme activity in cellular elements and in the neuropil. This increase in enzyme activity in brain capillaries continued up to the age of 12 months, when it was succeeded by a decrease in GGT activity to the level found at 3 months. GGT activity in the choroid plexi rose significantly (more than double) between the age of 5 weeks and 18 months and was a whole order higher than GGT activity in 10 other regions of the mouse brain, whose development displayed no pronounced changes in the activity of the enzyme. A single dose of dexamethasone, or adrenalectomy, were used to demonstrate any participation by steroid hormones in the regulation of GGT activity in the brain tissue. Of the two techniques, only adrenalectomy led to a statistically significant decrease in activity in brain and liver tissue, while the apparent increase in GGT activity after a single dose of dexamethasone was not statistically significant. |
