Although vasodilation is conventionally held to be the predominant mic
rovascular response to a wound, there has been no previous attempt to
actually quantitate skin blood flow within and in the neighborhood of
wounds. In particular, there has been no differentiation between sites
with primarily nutritive (NUTR) blood now and those with considerable
arteriovenous (AV) perfusion. We used our previously described model
of cutaneous blood flow in the rat to study the blood now response to
wounding. We measured skin blood flow at the centers and at the undist
urbed perimeters of wounds placed at the back, a NUTR site, and at the
paw, an AV site, in 11 Wistar Kyoto rats. Measurements were performed
at baseline, and then at 3 hr, 24 hr, 72 hr, and 7 days postwounding.
At 3 hr, now at the center of the back wound had increased to 11.3 +/
- 1.4 ml/min/100 g from a baseline of 2.1 +/- 0.1 ml/min/100 g and rem
ained elevated at 7 days (8.3 ml/min/100 g). Flow at the perimeter of
the back wound rose as well, but not as high as at wound center, to tw
ice the baseline level (4.1 ml/min/100 g at Day 7). Flow values at con
trol sites on the back did not increase from baseline. Flow at the cen
ter of the paw wound rose from 7.2 +/- 0.5 ml/min/100 g at baseline to
15.6 +/- 4.3 ml/min/100 g at Day 3 but then fell back to 6.9 +/- 0.9
ml/min/100 g at Day 7. There was only a very small increase in the bas
al temperature wound response at the paw perimeter. Blood now at all w
ound sites showed a response to heat. At the back, heating to 44 degre
es stimulated an 80%, increase in blood flow at baseline. This degree
of increase was maintained at both the center and the perimeter of the
back wound. In contrast, although there was also a thermal response a
t the paw wound center, it was of much lower magnitude than the nonwou
nded baseline response. As a result, the heat-stimulated now value act
ually fell over the 7 days to approximately half of the baseline level
. At the paw wound periphery, there was an initial fall in the heat st
imulated response, but it then recovered to the baseline level and rem
ained stable over the 7 days. Thus, the skin blood flow response seen
at the paw wound challenges the conventional concept of vasodilation a
s the expected wound blood flow response. The mechanisms of blood now
response in the healing wound may be more complex than the simple infl
ammatory vasodilation conventionally postulated. (C) 1997 Academic Pre
ss.