Localization of glutathione S-transferases alpha and pi in human embryonic tissues at 8 weeks gestational age.

Glutathione S-transferases (GST) are a family of enzymes involved in the detoxification of xenobiotics. In humans, GST are divided into four different classes, α, μ, π and 0, with partly overlapping substrate specificity and a tissue-specific expression pattern. We studied the cellular distribution of GST a and K in a variety of human embryonic organs obtained from an extra-uterine monozygotic twin pregnancy at 8 weeks' gestational age. Tissues were fixed in 4% paraformaldehyde and embedded in paraffin. Three 4 Clan thick sections were used, one for routine haematein and eosin staining, the others for immunohistochemical determination using monoclonal and polyclonal antibodies against GST α and π respectively. Both GST α and π were present in hepatocytes, gastrointestinal epithelium, adrenal gland medulla, and tela chorioidea in the telencephalon. GST π, but not α, was found in the epithelium of pancreatic and pulmonary glands, trachea, nephrons and urinary collecting ducts, as well as in the pia mater of the telencephalon and in developing nerve tissue in the gastrointestinal muscularis mucosae. In summary, we have demonstrated that immunoreactive protein for both GST α and π is expressed in the human embryo at 8 weeks' gestational age. The early expression of GST α and π in the epithelia of the urinary and digestive tracts and the respiratory system supports the importance of GST in the detoxification of potentially toxic or carcinogenic compounds. Our results suggest that the embryo itself is capable of detoxifying noxious compounds that are generated intracellularly or that cross the trophoblastic tissue.