Hemodynamic and microcirculatory changes during development of renal hypertension.
To study the progression of vessel loss (rarefaction) during the development of hypertension, a plastic window was chronically implanted over the biceps femoralis muscle of reduced renal mass (RRM) and sham-operated control (SOC) rats on a low-salt diet (0.4%). Blood pressure was measured directly via a catheter implanted in the femoral artery, and tissue blood flow was measured by laser-Doppler flowmetry before and after local topical application of sodium nitroprusside. Measurements were made on the control day and after an increase in sodium intake (4.0%) in RRM rats on days 5, 10, 14, 21, and 28. SOC rats on a low-salt diet served as the control group. RRM rats became hypertensive (167 mmHg), and vascular resistance increased after a change in sodium intake. Resting tissue blood flow decreased by 19% by day 28 in RRM but did not change in SOC. Sodium nitroprusside administration reduced vascular resistance to the same level in both RRM and SOC during control and at day 10; however, on all other days, sodium nitroprusside was not able to fully dilate the RRM microcirculation compared with that of SOC. At the same time, microvascular density estimated by computer fluorescence microscopy was decreased by 25% in RRM rats. These studies indicate that the development of RRM hypertension is characterized by a transition from increased tone and vessel closure (functional rarefaction) to anatomic vessel loss (structural rarefaction).
Hernandez
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Department of Physiology, Medical College of Wisconsin, Milwaukee 53226.
Greene
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D000704:Analysis of Variance; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D006439:Hemodynamics / Q000187:drug effects; D006977:Hypertension, Renal / Q000503:physiopathology*; D017078:Laser-Doppler Flowmetry; D008297:Male; D008833:Microcirculation / Q000187:drug effects / Q000502:physiology / Q000503:physiopathology*; D018715:Microscopy, Video; D009132:Muscles / Q000098:blood supply*; D009599:Nitroprusside / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012016:Reference Values; D012039:Regional Blood Flow / Q000187:drug effects; D013997:Time Factors; D014655:Vascular Resistance / Q000187:drug effects
D009599:Nitroprusside