The ultrastructure of radiation injury in rat lung: modification by D-penicillamine

The present study compared the ultrastructure of radiation injury in the lungs of penicillamine-treated and untreated male rats sacrificed 3, 6, 9, or 12 months after a single exposure of 25 Gy of 60Co #betta#-rays to the right hemithorax. All morphological components of the irradiated lungs exhibited injury typical of pneumonitis progressing to interstitial fibrosis. In addition to these well-documented responses, several less common ultrastructural changes were noted, including capillary recanalization; focal disappearance of interstitial collagen fibers, initially perivascularly, then throughout some septa; and a low-grade but significant cellular reaction in the shielded left lung. Radiation reactions in the lungs of penicillamine-treated rats were qualitatively similar to those of untreated animals, but differed in the degree of change: collagen deposition was less extensive and less highly organized into fibers, capillary recanalization and disappearance of interstitial collagen were more common, and arterial wall thickening was reduced in the drug-treated rats. Thus the beneficial effect of penicillamine on the histopathology of irradiated rat lung does not appear to be attributable to unique ultrastructural phenomena. Rather, penicillamine treatment produces a generalized inhibition of pathologic events such as collagen accumulation and arterial wall thickening, and acceleration of restorative processes such as revascularization and collagen degradation