Regulation ofP-450 4A activity in the glomerulus of the rat
We recently reported that an enzyme of the cytochrome P-450 4A family is expressed in the glomerulus, but there is no evidence that 20-hydroxyeicosatetraenoic acid (20-HETE) can be produced by this tissue. The purpose of present study was to determine whether glomeruli isolated from the kidney of rats can produce 20-HETE and whether the production of this metabolite is regulated by nitric oxide (NO) and dietary salt intake. Isolated glomeruli produced 20-HETE, dihydroxyeicosatrienoic acids, and 12-hydroxyeicosatetraenoic acid (4.13 ± 0.38, 4.20 ± 0.38, and 2.10 ± 0.20 pmol ⋅ min−1⋅ mg protein−1, respectively) when incubated with arachidonic acid (10 μM). The formation of 20-HETE was dependent on the availability of NADPH and the[Formula: see text] of the incubation medium. The formation of 20-HETE was inhibited by NO donors in a concentration-dependent manner. The production of 20-HETE was greater in glomeruli isolated from the kidneys of rats fed a low-salt diet than in kidneys of rats fed a high-salt diet (5.67 ± 0.32 vs. 2.83 ± 0.32 pmol ⋅ min−1⋅ mg protein−1). Immunoblot experiments indicated that the expression of P-450 4A protein in glomeruli from the kidneys of rats fed a low-salt diet was sixfold higher than in kidneys of rats fed a high-salt diet. These results indicate that arachidonic acid is primarily metabolized to 20-HETE and dihydroxyeicosatrienoic acids in glomeruli and that glomerular P-450 activity is modulated by NO and dietary salt intake.