Developmental formation and cortisol regulation of gamma-glutamyl transpeptidase in brain and spinal cord of chick embryo.

The developmentally conditioned changes in gamma-glutamyl transpeptidase (GGT) activity in chick embryonic hemispheres, optic lobes, cerebellum, brain stem and in lumbar and brachial enlargements of the spinal cord were studied. A marked increase in GGT activity was found in all tissues between embryonic day 11 and hatching. The application of cortisol enhanced GGT activity particularly on embryonic days 15 and 17. This effect of cortisol was reversed by the concomitant administration of actinomycin D or cycloheximide. The results are discussed in relation to the potential metabolic and transport role of GGT and its regulation in the developing chick embryonic brain.