Angiotensin II releases 20-HETE from rat renal microvessels

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Abstract
We studied hydroxyeicosatetraenoic acid (HETE) release in response to ANG II from preglomerular microvessels (PGMVs), the vascular segment governing changes in renal vascular resistance. PGMVs were isolated from Sprague-Dawley rats and incubated with NADPH and hormones at 37°C. Eicosanoids were extracted, and cytochrome P-450 (CYP)-derived HETEs were purified and quantitated by negative chemical ionization gas chromatography-mass spectroscopy. PGMVs produced primarily 20- and 19-HETEs, namely, 7.9 ± 1.7 and 2.2 ± 0.5 ng/mg protein, respectively. ANG II (5 nM) increased CYP-HETE release by two- to threefold; bradykinin, phenylephrine, and Ca2+ionophore were without effect. [Sar1]ANG II (0.1–100 μM) dose dependently stimulated 19- and 20-HETEs, an effect blocked by the AT2-receptor antagonist PD-123319 as well as by U-73122, a phospholipase C inhibitor. Microvascular 20-HETE release was increased more than twofold by the third day in response to ANG II (120 ng · kg−1· min−1) infused subcutaneously for 2 wk; it was not further enhanced after 14 days, although blood pressure continued to rise. Thus an AT2-phospholipse C effector unit is associated with synthesis of a vasoconstrictor product, 20-HETE, in a key renovascular segment.

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