[Immunohistochemical and biochemical investigations on glutathione S-transferases in the human placenta].

GST-pi can be purified as a major molecular form of glutathione S-transferase (GST) in human placenta. In this paper, the localization of GST-pi as well as of neutral and basic GSTs in the first, second and third trimester placental tissues (10, 3 and 14 samples, respectively) was investigated immunohistochemically using antibodies to acidic GST-pi from the placenta, neutral GST-mu and basic GST-I from the liver. Total GST activity was assayed using 1-chloro-2,4-dinitrobenzene as a substrate, and the relative activity and content of GST-pi were determined by activity inhibition test and single radial immunodiffusion, respectively, on 4 first and 5 third trimester placental tissues. The results obtained were as follows. In early placenta, cytotrophoblasts were strongly stained by anti-GST-pi antibody, while in third placenta mainly syncytiotrophoblasts were stained. GST-mu was stained only in syncytiotrophoblast in early placenta, while basic GST-I was weakly stained in the various cells in early to term placenta. Total GST activity in early and term placentas was 5.8 +/- 2.0 units/g of tissue (mean +/- S.D.) and 14.8 +/- 3.4 units/g, respectively. GST-pi relative activities were 90 +/- 4% and 85 +/- 6%, and GST-pi content was 41 +/- 31 micrograms/g and 106 +/- 29 micrograms/g, respectively. These results indicate that GST-pi is a major form of GST and localized mainly in trophoblasts at any developmental stage of the placenta, and it increases with development.