Submitted on April 12, 2005
Accepted on June 16, 2005
Renal 20-Hydroxyeicosatetraenoic Acid Inhibition Attenuates the Changes of Renal Hemodynamics Induced by N-nitro-L-arginine Methyl Ester Treatment in Pregnant Rats
Hui Huang1, Yiqiang Zhou2, Venugopal T. Raju3, Juan Du2, Hsin-Hsin Chang2, Cong-Yi Wang2, Michael W. Brands2, John R. Falck3, and Mong-Heng Wang2*
1 Department of Physiology and Renal Department of Memorial Hospital, Medical College of Georgia and Sun Yat-Sen University, Guangzhou, Province, China
2 Department of Physiology and Center for Biotechnology and Genomic Medicine, Medical College of Georgia, Augusta, GA, USA
3 Department of Biochemistry and Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX, USA
* To whom correspondence should be addressed. E-mail: mwang{at}mail.mcg.edu.
We previously reported that inhibition of nitric oxide (NO) synthesis by NG-nitro-arginine methyl
ester (L-NAME) during late pregnancy leads to increased production of renal vascular 20-
hydroxyeicosatetraenoic acid (20-HETE), a cytochrome P-450 (CYP) 4A-derived vasoconstrictor, in
pregnant rats. However, the effect of up-regulation of vascular 20-HETE production on renal function
after NO inhibition is not known. To test the hypothesis that increased gestational vascular 20-HETE
synthesis after NO inhibition is involved in mediating blood pressure and renal functional changes, we
first determined the IC50 value of the effect of nitroprusside (SNP), a NO donor, on renal 20-HETE
production in cortical microsomes. We then divided pregnant rats and age-matched virgin rats into a
vehicle control group, an L-NAME treatment group (0.25 mg/mL in drinking water), and a group treated
with L-NAME plus N-methylsulfonyl-12, 12-dibromododec-11-enamide (DDMS, CYP4A selective
inhibitor, 10 mg/kg/day, iv). After 4 days of treatment, we measured blood pressure (BP), renal blood
flow (RBF), renal vascular resistance (RVR), and glomerular filtration rate (GFR) in each group. The
addition of SNP (IC50 = 22 µM) decreased renal cortical 20-HETE production. In pregnant rats, L-NAME
treatment led to significantly higher mean arterial pressure (MAP) and RVR, and lower RBF and
GFR. Combined treatment with DDMS and L-NAME significantly attenuated the increases in MAP and
RVR and the decrease in GFR, but not the reduction in RBF induced by L-NAME treatment. L-NAME
and L-NAME plus DDMS had no significant impact on renal hemodynamics in virgin rats. In addition,
chronic treatment with DDMS selectively inhibited cortical 20-HETE production without a significant
effect on CYP4A expression in L-NAME-treated pregnant rats. In conclusion, NO effectively inhibits
renal cortical microsomal 20-HETE production in female rats. In pregnant rats, that the augmentation of
renal 20-HETE production after NO inhibition is associated with increased MAP and RVR, while
decreased GFR is negated by treatment of a selective and competitive CYP4A inhibitor. These results demonstrate that the interaction between renal 20-HETE and NO is important in the regulation of renal
function and blood pressure in pregnant rats.
