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Invited Symposium: Hypertension II: Hypertension and Vascular Control






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Effect Of Dietary Salt On Myogenic Responsiveness Of Proximal Arterioles And Local Nitric Oxide In Normotensive And Hypertensive Rats

Nurkiewicz, T.R. (Department of Physiology, West Virginia University School of Medicine, USA)
Boegehold, M.A. (Department of Physiology, West Virginia University School of Medicine, USA)

Contact Person: Timothy R. Nurkiewicz (tnurkiew@wvu.edu)


Abstract

The aims of this study were to determine if hypertension and/or high salt intake can alter the myogenic behavior of proximal arterioles in striated muscle, and to assess the modulation of this behavior by endogenous nitric oxide (NO). Wistar-Kyoto (WKY) and spontaneously hypertensive rats (SHR) fed low-salt (0.45%, LS) or high-salt (7%, HS) diets were enclosed in a ventilated airtight box with the spinotrapezius muscle exteriorized for intravital microscopy. Mean arterial pressure was resistant to dietary salt in WKY (LS: 966 mm Hg, HS: 9811 mm Hg), whereas it was significantly higher and augmented by dietary salt in SHR (LS: 1634 mm Hg, HS: 2053 mm Hg). Resting arteriolar diameters (D, 403 to 474 mm), wall shear rates (WSR, 57944 to 728132 s-1) and volume flows (Q, 41 to 71 nl/s) were not different among groups. In all groups, box pressurization to 30 mm Hg caused the same increase in arteriolar transmural pressures (servo-null method), resulting in immediate arteriolar constriction. These myogenic responses were similar in WKY and SHR (constrictions of 192% in WKY-LS vs 175% in SHR-LS). High salt intake reduced myogenic responses in WKY (75% constriction) but not in SHR (275% constriction). Constriction magnitude did not correlate with resting WSR or Q in any group, and constriction was sustained despite secondary increases in WSR and decreases in Q. Inhibition of NO synthesis (NG-monomethyl-L-arginine) augmented myogenic responses to a similar extent in WKY-LS (363%) and SHR-LS (356%.), but had no effect in WKY-HS or SHR-HS. Therefore, high dietary salt may alter local blood flow control by suppressing (1) the myogenic activity of proximal arterioles in normotensive rats, and (2) the influence of NO on this activity in normotensive and hypertensive rats. (Supported by NIH HL-44012 and HL-52019

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Presentation Number SAnurkiewicz0617
Keywords: myogenic response, microcirculation, nitric oxide, dietary salt, hypertension


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Nurkiewicz, T.R.; Boegehold, M.A.; (1998). Effect Of Dietary Salt On Myogenic Responsiveness Of Proximal Arterioles And Local Nitric Oxide In Normotensive And Hypertensive Rats. Presented at INABIS '98 - 5th Internet World Congress on Biomedical Sciences at McMaster University, Canada, Dec 7-16th. Invited Symposium. Available at URL http://www.mcmaster.ca/inabis98/boegehold/nurkiewicz0617/index.html
© 1998 Author(s) Hold Copyright