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Diameter changes in skeletal muscle venules during arterial pressure reduction
J J Bishop1, P R Nance, A S Popel
1Department of Bioengineering, University of California, San Diego, La Jolla, California 92093, USA.
Summary
Venules in skeletal muscle showed minimal diameter changes during arterial pressure reduction. These findings suggest venular collapse is unlikely to significantly increase venous resistance.
Area of Science:
- Physiology
- Microcirculation
- Vascular Biology
Background:
- Previous studies indicated significant increases in venous vascular resistance with arterial pressure reduction in skeletal muscle.
- Microcirculatory studies previously showed no venular diameter changes in the horizontal direction during arterial pressure reduction.
Purpose of the Study:
- To investigate the potential for venular collapse in the vertical direction within skeletal muscle microcirculation.
- To quantify venular diameter changes during acute arterial pressure reduction.
Main Methods:
- Utilized a vertically mounted rat spinotrapezius muscle preparation with a horizontally placed microscope.
- Monitored venule diameters (horizontal and vertical orientations) using a video system during hemorrhage-induced arterial pressure reduction.
- Assessed venular response after inducing red blood cell aggregation with Dextran 500.
Main Results:
- Small but statistically significant reductions in venular diameters were observed in both horizontal (1.0 ± 2.5 µm) and vertical (1.8 ± 3.1 µm) orientations.
- Arterial pressure was reduced from 115.0 ± 26.3 mmHg to 39.8 ± 12.3 mmHg.
- Venular responses did not differ after red blood cell aggregation.
Conclusions:
- Venular diameter changes during acute arterial pressure reduction are isotropic.
- The observed diameter changes suggest a minimal (<10%) increase in venous resistance.
- Venular collapse is unlikely to be a major factor in increased venous resistance during moderate arterial pressure reduction.