• Hypertension · Jan 1998

    Protective effect of angiotensin II-induced increase in nitric oxide in the renal medullary circulation.

    • A P Zou, F Wu, and A W Cowley.
    • Department of Physiology, Medical College of Wisconsin, Milwaukee 53226, USA. azou@post.its.mcw.edu
    • Hypertension. 1998 Jan 1;31(1 Pt 2):271-6.

    AbstractThis study examined the effect of intravenous infusion of subpressor doses of angiotensin (Ang II) on renal medullary blood flow (MBF), medullary partial oxygen pressure (PO2), and nitric oxide (NO) concentration under normal conditions and during reduction of the medullary nitric oxide synthase (NOS) activity in anesthetized rats. With laser Doppler flowmetry and polarographic measurement of PO2 with microelectrodes, Ang II (5 ng/kg per minute) did not alter renal cortical and medullary blood flows or medullary PO2. N(omega)-nitro-L-arginine methyl ester (L-NAME) was infused into the renal medullary interstitial space at a dose of 1.4 microg/kg per minute, a dose that did not significantly alter basal levels of MBF or PO2. Intravenous infusion of Ang II at the same dose in the presence of L-NAME decreased MBF by 23% and medullary PO2 by 28%, but it had no effect on cortical blood flow or arterial blood pressure. An in vivo microdialysis-oxyhemoglobin NO trapping technique was used in other rats to determine tissue NO concentrations using the same protocol. Ang II infusion increased tissue NO concentrations by 85% in the renal cortex and 150% in the renal medulla. Renal medullary interstitial infusion of L-NAME (1.4 microg/kg per minute) reduced medullary NO concentrations and substantially blocked Ang II-induced increases in NO concentrations in the renal medulla, but not in the renal cortex. Tissue slices of the renal cortex and medulla were studied to determine the effects of Ang II and L-NAME on the nitrite/nitrate production. Ang II stimulated the nitrite/nitrate production predominately in the renal medulla, which was significantly attenuated by L-NAME. We conclude that small elevations of circulating Ang II levels increase medullary NO production and concentrations, which plays an important role in buffering the vasoconstrictor effects of this peptide and in maintaining a constancy of MBF.

      Pubmed     Free full text   Copy Citation     Plaintext  

      Add institutional full text...

    Notes

     
    Knowledge, pearl, summary or comment to share?
    300 characters remaining
    help        
    You can also include formatting, links, images and footnotes in your notes
    • Simple formatting can be added to notes, such as *italics*, _underline_ or **bold**.
    • Superscript can be denoted by <sup>text</sup> and subscript <sub>text</sub>.
    • Numbered or bulleted lists can be created using either numbered lines 1. 2. 3., hyphens - or asterisks *.
    • Links can be included with: [my link to pubmed](http://pubmed.com)
    • Images can be included with: ![alt text](https://bestmedicaljournal.com/study_graph.jpg "Image Title Text")
    • For footnotes use [^1](This is a footnote.) inline.
    • Or use an inline reference [^1] to refer to a longer footnote elseweher in the document [^1]: This is a long footnote..

    hide…