Journal
AMERICAN JOURNAL OF PHYSIOLOGY-HEART AND CIRCULATORY PHYSIOLOGY
Volume 280, Issue 1, Pages H222-H236Publisher
AMER PHYSIOLOGICAL SOC
DOI: 10.1152/ajpheart.2001.280.1.H222
Keywords
venous resistance; blood constitutive equation; in vivo blood viscosity; in vivo fluorescence microscopy; wall shear stress
Funding
- NATIONAL HEART, LUNG, AND BLOOD INSTITUTE [R01HL052684, R56HL052684] Funding Source: NIH RePORTER
- NHLBI NIH HHS [HL-52684] Funding Source: Medline
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A recent whole organ study in cat skeletal muscle showed that the increase in venous resistance seen at reduced arterial pressures is nearly abolished when the muscle is perfused with a nonaggregating red blood cell suspension. To explore a possible underlying mechanism, we tested the hypothesis that red blood cell aggregation alters flow patterns in vivo and leads to blunted red blood cell velocity profiles at reduced shear rates. With the use of fluorescently labeled red blood cells in tracer quantities and a video system equipped with a gated image intensifier, we obtained velocity profiles in venous microvessels (45-75 mum) of rat spinotrapezius muscle at centerline velocities between 0.3 and 14 mm/s (pseudo-shear rates 3-120 s(-1)) under normal (nonaggregating) conditions and after induction of red blood cell aggregation with Dextran 500. Profiles are nearly parabolic (Poiseuille flow) over this flow rate range in the absence of aggregation. When aggregation is present, profiles are parabolic at high shear rates and become significantly blunted at pseudoshear rates of 40 s(-1) and below. These results indicate a possible mechanism for increased venous resistance at reduced flows.
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