LOCALIZATION OF GLUTATHIONE-S-TRANSFERASE-ALPHA AND GLUTATHIONE-S-TRANSFERASE-PI IN HUMAN EMBRYONIC-TISSUES AT 8 WEEKS GESTATIONAL-AGE

Glutathione S-transferases (GST) are a family of enzymes involved in t he detoxification of xenobiotics, In humans, GST are divided into four different classes, alpha, mu, pi and theta, with partly overlapping s ubstrate specificity and a tissue-specific expression pattern. We stud ied the cellular distribution of GST alpha and pi in a variety of huma n embryonic organs obtained from an extra-uterine monozygotic twin pre gnancy at 8 weeks' gestational age. Tissues were fixed in 4% paraforma ldehyde and embedded in paraffin, Three 4 mu m thick sections were use d, one for routine haematein and eosin staining, the others for immuno histochemical determination using monoclonal and polyclonal antibodies against GST alpha and pi, respectively. Both GST alpha and pi were pr esent in hepatocytes, gastrointestinal epithelium, adrenal gland medul la, and tela chorioidea in the telencephalon. GST pi, but not alpha, w as found in the epithelium of pancreatic and pulmonary glands, trachea , nephrons and urinary collecting ducts, as well as in the pia mater o f the telencephalon and in developing nerve tissue in the gastrointest inal muscularis mucosae, In summary, we have demonstrated that immunor eactive protein for both GST alpha and pi is expressed in the human em bryo at 8 weeks' gestational age, The early expression of GST alpha an d pi in the epithelia of the urinary and digestive tracts and the resp iratory 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 ar e generated intracellularly or that cross the trophoblastic tissue.