IMMUNOHISTOCHEMICAL DETECTION OF PROSTAGLANDINS E(2), F2-ALPHA AND 6-KETO-PROSTAGLANDIN F1-ALPHA IN EXPERIMENTALLY-INDUCED PERIAPICAL INFLAMMATORY LESIONS IN RATS

The immunohistochemical localization of prostaglandin (PG) E(2), PGF(2 alpha), and 6-keto-PGF(1 alpha) (a stable metabolite of PGI(2)) was d emonstrated in rat periapical inflammatory lesions induced by opening the pulp chamber. Two wk postoperatively, suppurative periapical lesio ns were formed, and active bone resorption was seen surrounding these lesions. Immunohistochemical examination showed that macrophages infil trating in inflammatory tissue were positively stained for the examine d PGs. In some lesions, wherein acute inflammatory changes subsided an d proliferation of fibroblasts started, the fibroblasts were positivel y stained for 6-keto-PGF(1 alpha). Osteocytes and osteoblasts were als o positive for 6-keto-PGF(1 alpha) not only in experimental animals, b ut also in untreated animals. However the staining intensity of the PG in these cells was higher in periapical lesions than in normal condit ion. These findings suggested that the cellular sources of the PGs in the periapical lesions are mainly macrophages and fibroblasts, and tha t the PGs produced by these cells, and possibly osteoblasts and osteoc ytes, may contribute to the osteolytic resorption of periapical lesion s.