AJP - Heart and Circulatory Physiology, Vol 256, Issue 1 126-H131, Copyright © 1989 by American Physiological Society
Microvascular rarefaction and tissue vascular resistance in hypertension
A. S. Greene, P. J. Tonellato, J. Lui, J. H. Lombard and A. W. Cowley Jr
Department of Physiology, Medical College of Wisconsin, Milwaukee 53226.
The purpose of this study was to quantitatively estimate the relative
contribution of arteriolar rarefaction (disappearance of microvessels) and
arteriolar constriction to the increases in total peripheral resistance and
changes in the patterns of flow distribution observed in hypertension. A
mathematical model of the hamster cheek pouch intraluminal microcirculation
was constructed based on data from the literature and observations from our
own laboratory. Separate rarefaction and constriction of third-order (3A)
and fourth-order (4A) arterioles were performed on the model, and the
results were quantified based on the changes of the computed vascular
resistance. The degree of increase in resistance depended both on the
number and the order of vessels rarefied or constricted and also on the
position of those vessels in the network. The maximum increases in
resistance obtained in the model runs were 21% for rarefaction and 75% for
constriction. Rarefaction, but not constriction, produced large increases
in the degree of heterogeneity of blood flow in the various vessel orders.
These results demonstrate that vessel rarefaction significantly influences
tissue blood flow resistance to a degree comparable with vessel
constriction; however, unlike constriction, microvascular rarefaction
markedly altered blood flow distribution in our model of the hamster cheek
pouch vascular bed. These findings conform with the hypothesis that a
significant component of the increase in total peripheral resistance in
hypertension may be due to vessel rarefaction.
