Quantitative observations of the acute effects of x-irradiation on brain capillary permeability. Part I

Rats were irradiated with single and multiple daily dose fractions of 200 to 2500 rad; the capillary permeability coefficients (P) for 14C-urea, 3H-glactitol, 3H-VM-26, and bleomycin were determined after completion of each course. The drugs have a wide range of molecular weights and lipophilicities. Radiation doses of 200 rad x 5 days and 400 rad x 1 day increased the urea P 14 to 32%, while other dose fractions had no effect on P. The P for galactitol was increased more consistently (52 to 116%) by single and multiple 200 rad fractions and single fractions of 400 and 1000 rad. The P for galactitol paradoxically was reduced approximately 60% by 200 rad x 10 days and 2500 rad x 1 day fractions. Permeability to galactitol was determined at various times 3 to 24 hr after single radiation doses of 200, 400, and 1000 rad; at all times P was increased over nonirradiated animals. No radiation dose had an effect on the P for bleomycin. Except for a single fraction (400 rad x 1 day), the P for VM-26 was also unaffected by radiation, and in that instance the P was reduced from normal