Immunolocalization of cellular glutathione peroxidase in adult rat lungs and quantitative analysis after postembedding immunogold labeling

To determine the distribution of cellular glutathione peroxidase in rat lungs, the tissues were stained immunohistochemically. Quantitative analysis was performed in certain cell types of alveolar linings, after the ultrathin sections were stained by a postembedding immunogold technique. Immunoblot analysis revealed that homogenates of rat liver, heart, and lungs all gave a single band. Under the light microscope, the following tissues were stained intensely: epithelial cells, smooth muscle cells and glands of bronchi and bronchioles, type II alveolar cells, and alveolar macrophages. Under immunoelectron microscopy, type II alveolar cells and macrophages were abundant in mitochondria. The mitochondria, nucleus, and cytoplasm of macrophages were labeled almost twice as densely as the respective compartments of type II alveolar cells. Within cell types, the mitochondria were labeled twice as densely as the nuclei. The other particles were less than half as densely labeled as the nuclei. The labeling was slightly less dense in the cytoplasm than in the nucleus. The present study revealed that glutathione peroxidase occurred predominantly in the epithelial linings and metabolically active sites in rat lungs. The tissues that were previously found to be rich in superoxide dismutases were also rich in glutathione peroxidase.