Vascular injury in the mouse rectum after irradiation and cis-diamminedichloroplatinum (II)

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Abstract
The rectum is a major critical organ in the radiation treatment of pelvic tumours in patients. Late radiation-induced lesions such as ulceration, stenosis, fibrosis and fistulae can be both severe and distressing and are extremely difficult to treat. A better understanding of the pathogenesis of radiation damage in this organ might provide clues towards therapeutic possibilities to prevent such injury. Suitable animal models have been developed (Black et al, 1980; Hubmann, 1981; Terry et al, 1983). It has been suggested that radiation damage in the microvasculature plays a key role in the onset of late damage in the rectum (Trott, 1984; Breiter & Trott, 1986). The present experiments were aimed at investigating functional changes in the rectal microvasculature at various times after irradiation given with or without cisdiamminedichloroplatinum (II) (c-DDP). These results were related to previously published histological alterations after such treatment (Dewit et al, 1987). Specific pathogen-free inbred male C3H/nu mice were used at an age of 12–20 weeks and a weight of 29–35 g. They were housed eight to 10 to a cage and fed laboratory chow and water ad libitum. Feeding conditions were not changed during observation period. Unanaesthetised mice were irradiated through one posterior field while immobilised in the prone position in acrylic plastic (Perspex) jigs as previously described (Dewit et al, 1987). The field size was 18.2 mm long by 22.0 mm wide, carefully chosen to include the descending colon, rectum and anus, and yet to exclude all small-bowel loops.