Activities of Cytosolic Glutathione Peroxidase and Phospholipid Hydroperoxide Glutathione Peroxidase in Rat Salivary Glands

Distribution of cytosolic glutathione peroxidase( cGPx)activity and phospholipid hydroperoxide glutathione peroxi- dase( PHGPx)was observed in rat salivary glands. Among three major glands, high cGPx activity was observed in submandibular and sublingual glands; activity in the parotid gland was about30% that of other glands. In intracellu- lar fractions, cGPx activity was mainly distributed in the cytosolic fraction. On the other hand, PHGPx activity was in the following order: submandibular, parotid and sublingual glands. PHGPx activity in the sublingual gland was rela- tively lower than the other glands in contrast to cGPx activity. PHGPx activity was widely distributed in cytosolic, mi- tochondrial and microsomal fractions. Activities in parotid mitochondrial and sublingual cytosolic fractions were rela- tively lower than the other fractions, although those in the submandibular gland were almost the same among the three fractions. In addition, PHGPx activities in both cytosolic and mitochondrial fractions showed less preference toward the phospholipid head-group, which is effective for the reduction of various phospholipid hydroperoxides formed in cells. The gland-specific distribution of cGPx and PHGPx may be caused by differences in oxygen consumption de- pending on saliva-secretory ability and distribution of PHGPx isozymes. In addition, it is suggested that cGPx and PHGPx in salivary glands share a role in the reduction of hydroperoxide as an antioxidant; cGPx reduces hydrophilic hydroperoxide in cytosol but PHGPx reduces phospholipid hydroperoxide in various compartments of cells.