LOCALIZATION OF ANTI-ALLERGIC AGENT IN RAT MAST CELLS DEMONSTRATED BY LIGHT AND ELECTRON MICROSCOPIC RADIOAUTOGRAPHY

In order to demonstrate the intracellular localization of anti-allergic agent in rat mast cells, 3H-labeled Tranilast, N-(3', 4'-dimethoxycinnamoyl) anthranilic acid was studied by both light and electron microscopic radio-autography.The peritoneal mast cells of several Wistar strain rats were collected and incubated in vitro with Tranilast (100μM) after sensitization with IgE and challenging with an antigen, demonstrating the inhibition of degranulation by type I allergic reaction. Then, the peritoneal mast cells were incubated in vitro with 3H-Tranilast (100μCi/ml) for varying time intervals from 0 to 60min and the cell pellets were fixed, embedded and processed for light and electron microscopic radioautography. Light microscopic radioautograms revealed that silver grains were localized over the cytoplasm. Electron microscopic radioautograms revealed that silver grains were localized over and around the granules. The number of silver grains increased according to the prolongation of incubation time.Several rats were administered orally with 3H-Tranilast (53μCi/gm body weight). They were sacrificed at various time intervals and the back skins were taken out, fixed, embedded and processed for light and electron microscopic radioautography. Silver grains were observed to localize over the subcutaneous tissues, especially concentrating over the mast cells.From the results, it is concluded that 3H-Tranilast was rapidly taken into mast cells in both in vitro and in vivo and it inhibited degranulation of type I allergic reaction.