Missing links: Cytochrome P450 arachidonate products A new class of lipid mediators.

Three major enzyme systems-cyclooxygenases, lipoxygenases, and cytochrome P450 monooxygenases (CYP)-generate biological mediators from arachidonic acid (AA). A distinct profile of arachidonate products characterizes each renal tubular segment and each section of the renal vascular tree from arteries to microvessels to veins. The most recent discoveries on renal mechanisms subserved by arachidonate metabolites relate to CYP pathways of AA metabolism. These arachidonate products have prominent effects on blood vessels and ion transport, including modulation and mediation of the actions of vasoactive hormones. The diverse properties of these AA metabolites and the wide distribution of the CYP system make them prime candidates for participation in regulatory mechanisms that affect the circulation and transporting epithelia. CYP-AA products are as important to renal and circulatory control as are nitric oxide and prostaglandins.