Cytochrome P450 expression and catalytic activity in coronary arteries and liver of cattle.

There is increasing evidence that cytochrome P450 (CYP) enzymes are involved not only in the metabolism of xenobiotics, but also in vascular homeostasis. Among the CYP-derived vasoactive agents, special importance is assigned to endogenous products from arachidonic acid (AA). Specifically, the vasodilator epoxyeicosatrienoic acids (EETs), being linked to the CYP 2B, 2C, and 2J subfamilies, and the vasoconstrictor 20-hydroxyeicosatetraenoic acid (20-HETE) connected instead to the CYP 4A subfamily and, to a lesser degree, to isoforms of the CYP 1A and 2E subfamilies. Here, we have examined the occurrence of functional CYP isoforms in the coronary arteries of cattle by RT-PCR with sequence verification, Western immunoblotting, and analysis of distinct catalytic activities with fluorescent substrate probes. Liver tissue was examined comparatively. Coronary tissue expressed mRNA transcripts and immunoreactive proteins belonging to the CYP 1A, 2C, 2E, and 2J subfamilies. Appropriate catalytic activity was ascertained with all these CYP species except 2J. A broader spectrum of CYP enzymes (CYP 1A, 2B, 2C, 2D, 2E, 2J, 3A, 4A subfamilies) was found in liver tissue with catalytic activities exceeding many fold those of coronary tissue. We conclude that bovine coronary arteries are endowed with a full-fledged CYP system with potential for AA-linked vasoregulation through dilator rather than constrictor agents. The same tissue and, to a much larger degree, liver tissue possess the capability of metabolizing xenobiotics via the CYP pathway.