FORMATION AND ACTIONS OF 20-HYDROXYEICOSATETRAENOIC ACID IN RAT RENALARTERIOLES

The present study examined whether preglomerular arterioles of the rat produce 20-hydroxyeicosatetraenoic acid (20-HETE) and whether 20-HETE is vasoactive on these vessels. Rat preglomerular arterioles produced 20-HETE (4.8 +/- 1.0 pmol . min(-1). mg(-1), n = 7) and, to a lesser extent, 14-, 15-, 11-, and 12-dihydroxyeicosatetraenoic acid, 6-ketopr ostaglandin F-1 alpha, and prostaglandin E(2) when incubated with [C-1 4]arachidonic acid. The results of immunoblotting and reverse-transcri ption polymerase chain reaction experiments indicate that these vessel s express mRNA and protein for a P-450 4A(2) enzyme. With the use of a rat juxtamedullary nephron microvascular preparation perfused in vitr o with a cell-free media, addition of 20-HETE (1 nM-1 mu M) to the bat h reduced the diameter of proximal and distal portions of the afferent arterioles. At a concentration of 1 mu M, the diameter of the proxima l and distal portions of the afferent arteriole fell by 14 +/- 1 and 1 6 +/- 3% after 20-HETE. The response to 20-HETE (1 mu M) was not alter ed by blockade of cyclooxygenase, lipoxygenase, and P-450 pathways. Bl ockade of the large-conductance Ca2+-activated K+ channel with tetraet hylammonium (1 mM) reduced the diameter of afferent arterioles by 10% and blocked the vasoconstrictor response to 20-HETE (1 mu M). These re sults indicate that 20-HETE is an endogenous constrictor of preglomeru lar arterioles and suggest a role for the P-450 4A(2) enzyme in the re gulation of renal vascular tone.