Blood Volume and Interstitial Fluid Pressure in the Development and Reversal of Renal Hypertension in Rats

1. During the development and maintenance of one-kidney, one-clip hypertension in rats, there were no significant differences in blood volume or interstitial fluid pressure compared with one-kidney control rats. 2. Rats with one-kidney, one-clip hypertension of 25 days' duration were either unclipped, sham-operated or nephrectomized. Over 24 h the changes in arterial pressure, blood volume and interstitial pressure in the sham and nephrectomized groups were insignificant. In the unclipped group arterial pressure decreased 50 mmHg to normal by 24 h and was associated with increased diuresis and a small decrease in blood volume (9.8%). Unclipped rats with the greatest urine outputs showed the largest decreases in interstitial pressure (r = 0.70, P<0.02). 3. Thus, in the reversal of this hypertension, changes in blood volume played only a partial role; decreased interstitial pressure was secondary to tissue fluid depletion from increased diuresis and normalization of arterial pressure required the presence of the unclipped kidney.

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Hypertension caused by salt loading. II: Fluid volume and tissue pressure changes

American Journal of Physiology-Legacy Content ◽

10.1152/ajplegacy.1964.207.3.669 ◽

1964 ◽

Vol 207 (3) ◽

pp. 669-671 ◽

Cited By ~ 47

Author(s):

Ben H. Douglas ◽

Arthur C. Guyton ◽

Jimmy B. Langston ◽

Vernon S. Bishop

Keyword(s):

Arterial Pressure ◽

Blood Volume ◽

Interstitial Fluid ◽

Salt Intake ◽

Fluid Pressure ◽

Renal Tissue ◽

Interstitial Fluid Pressure ◽

Experimental Hypertension ◽

Tissue Pressure ◽

Salt Loading

Experimental hypertension was produced in dogs by increasing their dietary intake of sodium chloride after removing approximately 70% of their renal tissue. The changes in mean arterial pressure, interstitial fluid pressure, blood volume, and sodium space were observed during the development and maintenance of the hypertension. During the periods of increased salt intake, the arterial pressure increased from a mean of 114.6 mm Hg to a mean of 150.6 mm Hg, and there were concomitant increases of 19.8% in blood volume, 16% in sodium space, and 4 cm H2O in interstitial fluid pressure. However, the increases in all the paramteers studied except arterial pressure were transient. The blood volume remained elevated above control values for a longer period of time than the sodium space and interstitial fluid pressure, but it reapproached normal after approximately 16–20 days.

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Dynamics of Interstitial Fluid Pressure in Extracellular Matrix Hydrogels in Microfluidic Devices

Journal of Biomechanical Engineering ◽

10.1115/1.4031020 ◽

2015 ◽

Vol 137 (9) ◽

Cited By ~ 5

Author(s):

Joe Tien ◽

Le Li ◽

Ozgur Ozsun ◽

Kamil L. Ekinci

Keyword(s):

Extracellular Matrix ◽

Pressure Distribution ◽

Interstitial Fluid ◽

Scaling Laws ◽

Fluid Pressure ◽

Interstitial Fluid Pressure ◽

External Loading ◽

Interstitial Pressure ◽

Time Resolved ◽

Long Time

In order to understand how interstitial fluid pressure and flow affect cell behavior, many studies use microfluidic approaches to apply externally controlled pressures to the boundary of a cell-containing gel. It is generally assumed that the resulting interstitial pressure distribution quickly reaches a steady-state, but this assumption has not been rigorously tested. Here, we demonstrate experimentally and computationally that the interstitial fluid pressure within an extracellular matrix gel in a microfluidic device can, in some cases, react with a long time delay to external loading. Remarkably, the source of this delay is the slight (∼100 nm in the cases examined here) distension of the walls of the device under pressure. Finite-element models show that the dynamics of interstitial pressure can be described as an instantaneous jump, followed by axial and transverse diffusion, until the steady pressure distribution is reached. The dynamics follow scaling laws that enable estimation of a gel's poroelastic constants from time-resolved measurements of interstitial fluid pressure.

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Interstitial Fluid Pressure: III. Its Effect on Resistance to Tissue Fluid Mobility

Circulation Research ◽

10.1161/01.res.19.2.412 ◽

1966 ◽

Vol 19 (2) ◽

pp. 412-419 ◽

Cited By ~ 98

Author(s):

ARTHUR C. GUYTON ◽

KONRAD SCHEEL ◽

DENNIS MURPHREE

Keyword(s):

Interstitial Fluid ◽

Fluid Pressure ◽

Interstitial Fluid Pressure ◽

Tissue Fluid

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Reevaluation of the needle method for measuring interstitial fluid pressure

American Journal of Physiology-Legacy Content ◽

10.1152/ajplegacy.1975.229.3.603 ◽

1975 ◽

Vol 229 (3) ◽

pp. 603-607 ◽

Cited By ~ 20

Author(s):

RA Brace ◽

AC Guyton ◽

AE Taylor

Keyword(s):

Interstitial Fluid ◽

Fluid Pressure ◽

Plateau Pressure ◽

Interstitial Fluid Pressure ◽

Continuous Recording ◽

Fluid Injection ◽

Tissue Fluid ◽

Equilibrium Pressure ◽

Anesthetized Dogs ◽

The Mean

Inserting a needle into subcutaneous spaces should allow a subatmospheric pressure to be measured if interstitial fluid pressure is truly negative as measured by the capsule and wick techniques. Previous needle measurements of interstitial fluid pressure have produced a positive value, but in most instances fluid has been injected into the tissues prior to recording of pressure. Therefore, we measured subcutaneous needle pressure in anesthetized dogs without fluid injection into the tissues. Approximately 30 min are required for an equilibrium pressure after insertion of the needle. The mean 30-min pressure was 4.6 +/- 0.5 (SE) mmHg (n equals 41). With observable edema, interstitial fluid pressures as measured with the needle were always positive. However, the needle method for continuous recording of pressure lacks rapid sensitivity to changes in tissue fluid pressures. In order to develop a needle method that would follow changes in interstitial fluid pressure, 0.5-1 mul of saline was injected into or withdrawn from the tissue. With this method, pressure plateaued in 10-20 min. This plateau pressure increased with tissue hydration and decreased with dehydration.

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