MORPHOLOGICAL AND HISTOCHEMICAL-CHANGES IN INTERCELLULAR JUNCTIONAL COMPLEXES IN EPITHELIAL-CELLS OF MOUSE SMALL-INTESTINE UPON X-IRRADIATION - CHANGES OF RUTHENIUM PERMEABILITY AND CALCIUM CONTENT

Changes of calcium-content and permeability of tight junction followin g X-irradiation were investigated in mouse intestinal epithelial cells by electron microscopy. In the control animals the lower parts of tig ht junctional area as well as the other junctional elements and the in tercellular space are labeled by pyroantimonate precipitates, which co ntain calcium as revealed by electron spectroscopy and electron energy loss spectrometry. X-irradiation, parallel with morphological changes , lead to rapid decrease of pyroantimonate precipitable calcium conten t and increase of the permeability of tight junctions indicated by the penetration of ruthenium red into the intercellular space. These chan ges were readily reversible following 0,5 Gy doses of irradiation howe ver, they persisted up to 24 hours following 5 Gy irradiation. We conc lude that irradiation at the applied doses can transiently destabilize the tight junctions in the epithelial layer of the small intestine, p resumably through a calcium dependent mechanism