Production of 20-HETE and its role in autoregulation of cerebral blood flow

In the brain, pressure-induced myogenic constriction of cerebral arteriolar muscle contributes to autoregulation of cerebral blood flow (CBF). This st udy examined the role of 20-HETE in autoregulation of CBF in anesthetized r ats. The expression of P-450 4A protein and mRNA was localized in isolated cerebral arteriolar muscle of rat by immunocytochemistry and in situ hybrid ization. The results of reverse transcriptase-polymerase chain reaction stu dies revealed that rat cerebral microvessels express cytochrome P-450 4A1, 4A2, 4A3, and 4A8 isoforms, some of which catalyze the formation of 20-HETE from arachidonic acid. Cerebral arterial microsomes incubated with [C-14]a rachidonic acid produced 20-METE. An elevation in transmural pressure from 20 to 140 mm Hg increased 20-METE concentration by 6-fold in cerebral arter ies as measured by gas chromatography/mass spectrometry. In vivo, inhibitio n of vascular 20-METE formation with N-methylsulfonyl-12,12-dibromododec-11 -enamide (DDMS), or its vasoconstrictor actions using 15-HETE or 20-hydroxy eicosa-6(Z),15(Z)-dienoic acid (20-HEDE), attenuated autoregulation of CBF to elevations of arterial pressure. In vitro application of DDMS, 15-HETE, or 20-HEDE eliminated pressure-induced constriction of rat middle cerebral arteries, and 20-HEDE and I5-HETE blocked the vasoconstriction action of 20 -HETE. Taken together, these data suggest an important role for 20-METE in the autoregulation of CBF.