Previous studies have shown that oxygen radical scavengers prevent the redu
ced cerebral blood flow that occurs following experimental traumatic brain
injury. The exact chemical species responsible for the posttraumatic reduct
ion in flow is unknown. We tested whether isoprostanes, which are formed by
non-cyclooxygenase-dependent free radical attack of arachidonic acid and a
re vasoconstrictors of the cerebral circulation, are increased in astrocyte
s following stretch-induced trauma or injury with a free radical generating
system. Isoprostane (8-epi-prostaglandin F-2 alpha) was analyzed in cells
and in media by immunoassay, Confluent rat cortical astrocytes in culture w
ere injured by a hydroxyl radical generating system consisting of hydrogen
peroxide and ferrous sulfate or by rapid stretch of astrocytes grown on a d
eformable silastic membrane. Some cells were treated with the iron chelator
deferoxamine for 1 h before injury. The hydroxyl generating system caused
free and cell-bound isoprostanes to increase to more than 400% of control.
After trauma, free and membrane bound isoprostanes increased to 321 +/- 34%
and 229 +/- 23% of control, respectively, and posttraumatic increases were
prevented by deferoxamine. Since astrocytes are in close proximity to cere
bral vessels, posttraumatic free radical formation may increase the formati
on of isoprostanes, which in turn produce vasoconstriction and decrease cer
ebral blood flow.