Si. Anderson et al., CAPILLARY RED-BLOOD-CELL FLOW AND ACTIVATION OF WHITE BLOOD-CELLS IN CHRONIC MUSCLE ISCHEMIA IN THE RAT, American journal of physiology. Heart and circulatory physiology, 41(6), 1997, pp. 2757-2764
Increased activity of ischemic skeletal muscles in which functional hy
peremia is impaired has been linked with capillary endothelial swellin
g and postcapillary white blood cell (WBC) adherence. The perfusion pa
ttern of capillaries under these conditions and the time course of WBC
activation is not known. Capillary microcirculation was studied by vi
deomicroscopy at rest and after muscle contractions (1 Hz, 10 min) in
extensor digitorum longus muscles of pentobarbital sodium-anesthetized
rats during the early stages of chronic ischemia (unilateral ligation
of the common iliac artery for 3 days) and in ischemic muscles subjec
ted to increased activity (7 days of ischemia or 3 days of ischemia pl
us indirect electrical stimulation via implanted electrodes, 10 Hz, 7
x 10 min on-90 min off/day) to investigate how perfusion was affected.
All ischemic muscles had more intermittently flowing capillaries than
did unoperated control muscles. Temporal heterogeneity of perfusion a
t rest, assessed by velocity, time spent stationary, and stop/ start f
requency of red blood cells, was similar to control values in ischemic
muscles but greater in ischemic muscles subjected to additional activ
ity. Hyperemic responses to contractions were severely blunted in all
ischemic groups. The proportion of morphologically nonspherical WBCs,
taken to indicate activation, was 24 +/- 3% in venous blood after 3 da
ys of ischemia vs. 14 +/- 1% in control muscles and increased further
by 7 days (42 +/- 2%) when activated cells were also found in arterial
blood. Thus increased muscular activity may exacerbate the adverse ef
fects of ischemia on capillary perfusion, and WBC activation, evident
before endothelial swelling is apparent, provides the potential as a c
irculating signal for capillary swelling in the ischemic and other mus
cles.