Faculty Collaboration Database

Renal medullary nitric oxide deficit of Dahl S rats enhances hypertensive actions of angiotensin II. Am J Physiol Regul Integr Comp Physiol 2002 Jul;283(1):R266-72

Date

06/19/2002

Pubmed ID

12069953

DOI

10.1152/ajpregu.00461.2001

Scopus ID

2-s2.0-0036340195 (requires institutional sign-in at Scopus site)   71 Citations

Abstract

Studies were designed to examine the hypothesis that the renal medulla of Dahl salt-sensitive (Dahl S) rats has a reduced capacity to generate nitric oxide (NO), which diminishes the ability to buffer against the chronic hypertensive effects of small elevations of circulating ANG II. NO synthase (NOS) activity in the outer medulla of Dahl S rats (arginine-citrulline conversion assay) was significantly reduced. This decrease in NOS activity was associated with the downregulation of protein expression of NOS I, NOS II, and NOS III isoforms in this region as determined by Western blot analysis. In anesthetized Dahl S rats, we observed that a low subpressor intravenous infusion of ANG II (5 ng. kg(-1). min(-1)) did not increase the concentration of NO in the renal medulla as measured by a microdialysis with oxyhemoglobin trapping technique. In contrast, ANG II produced a 38% increase in the concentration of NO (87 +/- 8 to 117 +/- 8 nmol/l) in the outer medulla of Brown-Norway (BN) rats. The same intravenous dose of ANG II reduced renal medullary blood flow as determined by laser-Doppler flowmetry in Dahl S, but not in BN rats. A 7-day intravenous ANG II infusion at a dose of 3 ng. kg(-1). min(-1) did not change mean arterial pressure (MAP) in the BN rats but increased MAP in Dahl S rats from 120 +/- 2 to 138 +/- 2 mmHg (P < 0.05). ANG II failed to increase MAP after NO substrate was provided by infusion of L-arginine (300 microg. kg(-1). min(-1)) into the renal medulla of Dahl S rats. Intravenous infusion of L-arginine at the same dose had no effect on the ANG II-induced hypertension. These results indicate that an impaired NO counterregulatory system in the outer medulla of Dahl S rats makes them more susceptible to the hypertensive actions of small elevations of ANG II.

Author List

Szentiványi M Jr, Zou AP, Mattson DL, Soares P, Moreno C, Roman RJ, Cowley AW Jr

Author

Allen W. Cowley Jr PhD Professor in the Physiology department at Medical College of Wisconsin

MESH terms used to index this publication - Major topics in bold

Angiotensin II
Animals
Arginine
Blood Pressure
Hypertension
Injections, Intravenous
Kidney Cortex
Kidney Medulla
Male
Nitric Oxide
Nitric Oxide Synthase
Osmolar Concentration
Rats
Rats, Inbred BN
Rats, Inbred Dahl
Regional Blood Flow
Vasoconstrictor Agents