Abstract
Distribution of leukocytes in rat mesenteric microvessel networks was studied using intravital fluorescence video microscopy. A digital image analysis system was used to measure vessel diameters, flow velocities and leukocyte fluxes in 306 capillaries of 8 networks. Capillaries were defined as vessel segments connecting divergent to convergent branch points. Their topological position within the network was quantified by a generation number defined as the number of bifurcations between the capillary and the arteriole feeding the network. Proximal capillaries (generation numbers 4 and 5) were slightly but significantly smaller in diameter (8.9±0.4) μm, mean ± SEM) than distal ones (generation numbers 20 and 21, 10.1±0.4 μm). Average capillary flow velocity decreased markedly from 2.0±1.0 mm·s-1 in proximal to 0.41 ±0.06 mm·s-1 in distal capillaries. Average leukocyte concentration was 3.4±0.5·109 l-1 and thus significantly below systemic values (6.0·109 l-1) in proximal capillaries, and above in distal ones (11.7±2.6·109l-1). The analysis of flow and leukocyte flux partition at 138 bifurcations showed preferential distribution of leukocytes to the daughter capillary with higher flow rate. This suggests a tentative explanation for the observed leukocyte accumulation along the microvascular tree: due to their low fractional flow, proximal capillaries draw relatively leukocytepoor blood from the arteriole feeding the network; this leads to an increased leukocyte concentration in distal capillaries. As a consequence of the concomitant increase of capillary diameter with increasing generation number, leukocytes are preferentially flowing through larger capillaries and are excluded from small ones.
Original language | English (US) |
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Pages (from-to) | 93-100 |
Number of pages | 8 |
Journal | Pflügers Archiv European Journal of Physiology |
Volume | 412 |
Issue number | 1-2 |
DOIs | |
State | Published - Jul 1988 |
Externally published | Yes |
Keywords
- Bifurcation
- Blood rheology
- Capillary
- Intravital microscopy
- Leukocytes
- Microcirculation
- Network
- Topology
ASJC Scopus subject areas
- Physiology
- Clinical Biochemistry
- Physiology (medical)