Oxygen radicals from arachidonate metabolism in abnormal vascular responses.

The involvement of oxygen radicals produced in association with arachidonate metabolism via PGH synthase in cerebral vascular responses is reviewed. PGH synthase generates superoxide in the presence of NADH or NADPH. Lipoxygenase also produces superoxide under similar conditions, but it is a much less important quantitative source for this radical. Radicals from the PGH synthase pathway are produced in vivo during topical application of arachidonate or bradykinin, a polypeptide that releases endogenous arachidonate from tissues. The vascular changes in response to arachidonate and bradykinin consist of functional, morphological, and biochemical alterations. Oxygen radicals from this pathway appear to play a role in the cerebral vascular changes in acute, severe hypertension and in fluid percussion brain injury.