TIGHT JUNCTIONAL CHANGES UPON MICROWAVE AND X-RAY IRRADIATION

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Abstract
Tight junctions (zonulae occludentes, ZO) are cellularly regulated dynamic structures sensitive to envi- ronmental stress agents including ionizing radiation. Radiation induced pathological alterations of the small intestine (gastrointestinal radiation syndrome) are related to altered ZO-mediated paracellular transport. We carried out a quantitative morphological evaluation of the murine jejunal epithelial tight junctional structure in freeze fracture replicas as changed upon whole body X-ray irradiation and low energy microwave exposition. X-ray treatment (4 Gy, 1, 24 h) brought about a partial dearrangement of the ZO strand network which regenerated only partially by 24 h. This observation is in line with data on paracellular permeability increases and ZO-bound calcium drop caused by X-ray irradiation. On the other hand, microwave treatment (16 Hz-modulated 2.45 GHz wave, 1 mW/cm 2 power density, 1 h exposition, samples at 1 and 3 h after exposition) did not cause dearrangement but, rather an increase in the integra- tion of thight junctional structure, which is in agreement with an increase in cytochemically detectable ZO-bound calcium