RADIOPROTECTION OF THE RAT INTESTINAL-MUCOSA BY TIRILAZAD

Purpose: To assess intestinal radioprotection by systemic or lumenal t irilazad mesylate and to test potential tumour radioprotection. Materi als and methods: Segments of the mid small bowel were surgically exter iorized. Tirilazad was given either intravenously or intralumenally 30 min prior to 11 Gy of X-irradiation to the exteriorized intestine. Ti ssues were harvested 5 days later to measure crypts per circumference and mucosal height. Potential tumour protection was assessed in a mous e sarcoma model. Tumours implanted in the hind limb were allowed to gr ow until a standard volume was attained, then irradiated (10 Gy) 30 mi n after intravenous (i.v.) administration of saline or tirilazad. Tumo ur growth was recorded for the next 22 days to determine if pretreatme nt with tirilazad interfered with radiation effects. Results: Systemic tirilazad provided no protection against intestinal damage and did no t alter tumour growth after irradiation. Topical tirilazad yielded hig hly significant protection of intestinal mucosa. Conclusions: These pr eliminary observations showed that topical tirilazad diminished radiat ion enteritis. Systemic drug had no effect on the severity of damage t o the intestine nor did it inhibit radiation effects on a tumour.