Alterations in free radical scavenging mechanisms following blood-brain barrier disruption

It has been reported earlier that rat microvessels which constitute the blood-brain barrier (BBB) are rich in free radical scavenging enzymes. In the present investigation, BBB of rat was disrupted by intravenous infusion of the hypertonic saline and changes in enzymes--namely, superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and glutathione reductase (GR)--were evaluated in the brain microvessels at 30 min after the intravenous administration of hypertonic saline, being the time of peak effect. There was a significant increase in the activities of CAT (40%), GPx (26%), and SOD (16%) over the control values. In addition, within 90 min BBB was found to be reestablished and the levels of enzymes reverted to normal. Malondialdehyde (MDA) levels and activity of lactate dehydrogenase (LDH) remained unaltered during and following disruption, suggesting that there was no change in the membrane lipid environment. Similarly, there was no cell lysis. The results suggest that the disruption of BBB following hypertonic saline administration might be due to an increase in the generation of free radicals in the brain microvessels.