• 1
    Cerebral arteries express cytochrome P450 4A enzymes (P450 4A) and produce 20- hydroxyeicosatetraenoic acid (20-HETE), a potent constrictor of pial arterioles. It is not known which cell type in the vessel wall is responsible for the formation of 20-HETE. We examined whether freshly isolated cerebral arterial muscle cells (VSMCs) express P450 4A and produce 20-HETE. We also studied the effect of 20-HETE on pressurized cerebral arteries and on whole-cell L-type Ca2+current (ICa) recorded in cat cerebral VSMCs.
  • 2
    Cat cerebral VSMCs incubated with [14C]arachidonic acid ([14C]AA) produced 20-HETE (3.9 ± 1.1 pmol min−1 (mg protein)−1).
  • 3
    Reverse transcription-polymerase chain reaction studies revealed that cat cerebral VSMCs express mRNA for P450 4A which metabolizes AA to 20-HETE. Cloning and sequencing of the cDNA amplified from mRNA isolated from VSMCs showed > 96 % amino acid homology to the rat and human P450 4A2 and 4A3.
  • 4
    20-HETE (1–300 nM) induced a concentration-dependent constriction of cat cerebral arteries, which was inhibited by nifedipine.
  • 5
    Addition of 10 and 100 nM 20-HETE to the bath increased peak ICa by 50 ± 3 and 100 ± 10 %, respectively. This effect was not influenced by altering the frequency of depolarization. 20-HETE (100 nM) failed to increase ICa in the presence of nifedipine.
  • 6
    These results demonstrate that cat cerebral VSMCs express P450 4A enzyme, and produce 20-HETE which activates L-type Ca2+ channel current to promote cerebral vasoconstriction.