Immunohistochemical detection of prostaglandins E2, F2 alpha, and 6-keto-prostaglandin F1 alpha in experimentally induced periapical inflammatory lesions in rats.

The immunohistochemical localization of prostaglandin (PG) E2, PGF2 alpha, and 6-keto-PGF1 alpha (a stable metabolite of PGI2) was demonstrated in rat periapical inflammatory lesions induced by opening the pulp chamber. Two wk postoperatively, suppurative periapical lesions were formed, and active bone resorption was seen surrounding these lesions. Immunohistochemical examination showed that macrophages infiltrating in inflammatory tissue were positively stained for the examined PGs. In some lesions, wherein acute inflammatory changes subsided and proliferation of fibroblasts started, the fibroblasts were positively stained for 6-keto-PGF1 alpha. Osteocytes and osteoblasts were also positive for 6-keto-PGF1 alpha not only in experimental animals, but also in untreated animals. However the staining intensity of the PG in these cells was higher in periapical lesions than in normal condition. These findings suggested that the cellular sources of the PGs in the periapical lesions are mainly macrophages and fibroblasts, and that the PGs produced by these cells, and possibly osteoblast and osteocytes, may contribute to the osteolytic resorption of periapical lesions.