Effects of free radicals and leukocytes on increases in blood-brain barrier permeability during colitis.

This study examined the role of leukocytes and free radicals on increases in permeability of the blood-brain barrier (BBB) in rabbits with acute colitis. Trinitrobenzene sulfonic acid (TNBS) was used to induce colitis in male New Zealand White rabbits. The extraction ratio of fluorescein was used as an index of the permeability of the BBB. The extraction ratio for fluorescein was 1.0 x 10(-3) +/- 2 x 10(-4) ml/g and 1.1 x 10(-3) +/- 3 x 10(-4)ml/g (mean +/- SE) for saline (N = 7) and ascorbic acid-treated (N = 8) rabbits with sham colitis. Conversely, TNBS-induced acute colitis increased the extraction ratio over 70% in saline (N = 8) and ascorbic acid-treated (N = 8) animals. Vinblastine significantly reduced the number of circulating leukocytes, whereas the permeability of the BBB was augmented by 54% in rabbits with TNBS-induced acute colitis (N = 8). Vinblastine had no effect on the permeability of the BBB in rabbits with sham colitis (N = 8). These data suggest that free radicals are not responsible for BBB disruption, and leukocytes may protect the BBB during acute colitis.