Increased Radiosensitivity of Cerebral Capillaries in Neonatal Gunn Rats as Compared to Sprague—Dawley Rats

Summary

The extent of petechial haemorrhages of the cerebral cortex examined between 14 hours and 4 days after X-irradiation to the head was compared in Sprague—Dawley and homozygous Gunn rats with congenital hyperbilirubinaemia. Animals 1 to 2 days old received single doses of either 250, 500 or 750 rad. By means of a special scoring scale the degree of the damage to the microvasculature was semi-quantitatively estimated. In both strains a significant difference in effect was obtained between 250 and 500 rad, but not between 500 and 750 rad. The shape of the dose—effect curve in Gunn rats was similar to that of Sprague—Dawley rats, but displaced upwards. In Gunn rats the effect of 250 rad was greater than that of 750 rad in Sprague—Dawley rats. Possible radiosensitizing mechanisms are discussed with reference to the literature and our results.