19-HETE is one of the major cytochrome P450 (CYP450) metabolites of arachidonic acid that is released from the kidney in response to angiotensin II. When formed by the CYP2E1 isoform, 19-HETE is composed of 70% and 30% of the (S) and (R) stereoisomers, respectively. Both 19(S)- and 19(R)-HETE are potent vasodilators of renal preglomerular vessels. However, 19(R)-HETE at 1 μM completely blocks 20-HETE-induced vasoconstriction of renal arterioles, whereas 19(S)-HETE remains inactive.