ULTRASTRUCTURAL OSTEOPONTIN LOCALIZATION IN PAPILLARY STONES INDUCED IN RATS

Objectives: To detect in situ the precise osteopontin (OPN) localizati on in papillary stones, Methods: Immunocytochemical labelling procedur es are applied to detect OPN localizations in crystalline material of renal papillary stones, The tissue-processing procedure for electron m icroscopy, which includes OsO4 postfixation, preserves both immunocyto chemical OPN reactivity and cellular membrane contrast up to the ultra thin section, Reflection-contrast light microscopical images are corre lated with high resolution transmission-electron microscopical observa tions from consecutive ultrathin epon sections, Results: Preserved cry stalline material in interstitial and peripheral papillary stones is r ecognized as calcium oxalate monohydrate. After section incubation wit h markers conjugated to an antibody against OPN (alpha OPN) the crysta ls are converted into ghosts. In the ghosts, alpha OPN markers are pre sent around microcrystals, The size of these microcrystals ranges from several nanometers to micrometers. It is observed (due to the OsO4-pr eserved membranes) that interstitial cells are separated from the ston e surfaces by unidentified extracellular material, also present in the center as a stone matrix, Conclusion: The microcrystal-growth inhibit or OPN is detected in situ in interstitial stones induced in the rat's papilla and at the surface of the papilla.