Late functional, biochemical and histological changes in the rat lung after fractionated irradiation to the whole thorax.
The influence of fractionation of the radiation dose in up to 16 fractions on late occurring effects in rat lungs was studied. Measurement of the breathing frequency (BF) was used to monitor changes in lung function during the 76-wk follow-up period. At the end of this period the lungs were examined histologically and the hydroxyproline (HP) content of the lung tissue was determined as a biochemical indicator of the amount of fibrosis. Dose-response curves for BF could only be made at 76 wk post-irradiation. No dose-response curves could be constructed for HP/mg dry tissue; dose-related increases observed in HP/total left lung were entirely attributable to increases in lung dry weight. Histopathology data indicated a dose-related increase in two histological alterations, septal fibrosis and granulomatous pneumonia. The alpha/beta ratios were calculated for each of the endpoints using both the Fe-plot and Direct Analysis method. The calculated values for alpha/beta were in the range of 1.1 to 3.6 Gy, corresponding well to published data obtained in mouse lungs. The number of tissue rescuing units (TRU's) was also calculated. It was smaller for BF than for the histopathology endpoints, suggesting different target structures. However, the difference was not significant due to large confidence intervals.
van Rongen
E
E
Radiobiological Institute TNO, Rijswijk, The Netherlands.
Tan
C H
CH
Durham
S K
SK
D000818:Animals; D004195:Disease Models, Animal; D004307:Dose-Response Relationship, Radiation; D005260:Female; D006909:Hydroxyproline / Q000032:analysis; D008168:Lung / Q000032:analysis / Q000473:pathology / Q000502:physiology / Q000528:radiation effects*; D011878:Radiotherapy / Q000009:adverse effects*; D051381:Rats; D011919:Rats, Inbred Strains; D012129:Respiratory Function Tests
D006909:Hydroxyproline