Expression and inducibility of alpha, pi, and mu glutathione S-transferaseprotein and mRNA in murine lung

This investigation sought to establish the cellular expression and distribu tion of the alpha, pi, and mu classes of glutathione S-transferase (GST) en zymes in murine lung under control conditions and after treatment with tert -butyl-4-hydroxyanisole (BHA). Immunohistochemical and in situ hybridizatio n studies were used to identify lung cells that were labeled for the GST su bunits Yp, Ya, and Yb-1. Immunoblotting of cytosolic proteins produced sing le bands of 28, 29, and 31 kD for Ya, Yp, and Yb-1, respectively, in sample s from untreated and BHA-treated mice. Treatment with BHA increased Ya and Yp reactivity, but this was not as marked for Yb-1. Immunohistochemical sta ining for the Yp, Ya, and Yb-1 subunits was localized in bronchioles and pa renchyma of untreated and BHA-treated mice. Bronchiolar Clara and alveolar type II cells were stained to the greatest extent for all of the GST subuni ts. BHA treatment produced increased staining that was most pronounced in t he bronchiolar epithelium. Ya and Yp were localized in the cytoplasm and nu cleus, whereas Yb, was found mainly in the cytoplasm. Immunoblots of extrac ted nuclear proteins revealed a band of 29 kD for Ya, with increased immuno reactivity in BHA-treated mice. In situ hybridization done with oligonucleo tide probes showed abundant silver grains representing Ya, Yp, and Yb, mess enger RNA (mRNA) transcripts in the bronchioles. Grains were also localized in alveolar septa, and were most numerous in type II cells. Quantitative i mage analysis confirmed good agreement between relative levels of protein a nd mRNA transcripts. Quantities of mRNA transcripts for all subunits were i ncreased in the parenchyma by BHA treatment, but the magnitudes of inductio n were most striking for Ya and Yp in the bronchioles. These results demons trated that Ya, Yp, and Yb-1 reside in specific lung areas and cells, and t hat in induced states, their increased expression is accompanied by increas ed mRNA.