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This Article Full Text Full Text (PDF) All Versions of this Article: 287/3/F535    most recent 00394.2003v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (6) Citing Articles via Google Scholar Google Scholar Articles by Zhang, Z. Articles by Pallone, T. L. Search for Related Content PubMed PubMed Citation Articles by Zhang, Z. Articles by Pallone, T. L.

Response of descending vasa recta to luminal pressure

Department of Medicine, Division of Nephrology, and Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland 21201-1595

Submitted 6 November 2003 ; accepted in final form 27 April 2004

We tested whether luminal perfusion and pressurization induce an endothelial cytoplasmic Ca²⁺ ([Ca²⁺]_CYT) response in descending vasa recta (DVR). DVR isolated from the rat outer medulla were cannulated and subjected to free-flow microperfusion (5 nl/min); the onset of which increased [Ca²⁺]_CYT from a baseline of 76 ± 13 to 221 ± 65 nM. A graded increase in luminal pressure from 0 to 45 mmHg in stopped-flow experiments induced a parallel increase in [Ca²⁺]_CYT from a baseline of 74 ± 24 to 194 ± 33 nM at 45 mmHg, with a tendency for [Ca²⁺]_CYT to plateau at pressures >25 mmHg. The removal of extracellular Ca²⁺ and blockade by either La³⁺ (10 µM) or SKF-96365 (100 µM) eliminated the response. Luminal pressurization to 25 mmHg increased nitric oxide (NO) generation, a response blocked by NO synthase inhibition or removal of extracellular Ca²⁺. The NO generation was not affected by the superoxide dismutase mimetic tempol. We conclude that DVR endothelia are mechanosensitive and respond to luminal pressure by elevating [Ca²⁺]_CYT and generating NO. That response might augment medullary perfusion and saliuresis.

medulla; kidney; microcirculation; shear; fura 2; 4,5-diaminofluoroscein

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