AJP - Gastrointestinal and Liver Physiology, Vol 247, Issue 6 617-G622, Copyright © 1984 by American Physiological Society
Differences in reactive hyperemia between the intestinal mucosa and muscularis
A. P. Shepherd and G. L. Riedel
In a previous study of regional intestinal blood flow by laser-Doppler
velocimetry, we noted that the mucosa displayed reactive hyperemia
following arterial occlusion but that the muscularis did not. Therefore, to
determine whether this observation is generally valid, we compared
responses of the mucosa and muscularis externa to arterial occlusion. We
measured total blood flow to isolated loops of canine small bowel with an
electromagnetic flow probe on the supply artery; blood flow either in the
mucosa or in the muscularis was measured by laser-Doppler velocimetry.
Mucosal and total blood flow consistently showed reactive hyperemia in
response to a 60-s occlusion, but the muscularis did not. To determine
whether metabolic rate influenced reactive hyperemia, we increased enteric
oxygen uptake by placing 5% bile and transportable solutes in the lumen;
these agents increased oxygen consumption by 36%. After a 60-s occlusion,
the durations of both total and mucosal reactive hyperemia were
significantly prolonged by increased metabolic rate. Similarly, the
payback-to-debt ratios in both total and mucosal blood flows were
significantly increased at elevated metabolic rate. These data support the
conclusions that reactive hyperemia occurs more frequently and has a
greater magnitude in the mucosa compared with the muscularis and both total
and mucosal reactive hyperemia are strongly influenced by the preocclusive
oxygen demand. These findings therefore constitute further evidence that
metabolic factors contribute to reactive hyperemia in the intestinal
circulation.
