Cat cerebral arterial smooth muscle cells express cytochrome P450 4A2 enzyme and produce the vasoconstrictor 20-HETE which enhances L-type Ca2+ current

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 Ca 2+ current ( I Ca ) recorded in cat cerebral VSMCs. Cat cerebral VSMCs incubated with [ 14 C]arachidonic acid ([ 14 C]AA) produced 20-HETE (3.9 ± 1.1 pmol min −1 (mg protein) −1 ). 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. 20-HETE (1–300 n m ) induced a concentration-dependent constriction of cat cerebral arteries, which was inhibited by nifedipine. Addition of 10 and 100 n m 20-HETE to the bath increased peak I Ca by 50 ± 3 and 100 ± 10%, respectively. This effect was not influenced by altering the frequency of depolarization. 20-HETE (100 n m ) failed to increase I Ca in the presence of nifedipine. These results demonstrate that cat cerebral VSMCs express P450 4A enzyme, and produce 20-HETE which activates L-type Ca 2+ channel current to promote cerebral vasoconstriction.