Microvascular pressures in the intestinal arteries, submucosal arterioles, and mucosal venules were measured in rats and rabbits at rest and during maximum dilation. From these data and Doppler velocimetry measurements of relative changes in whole organ blood flow on maximum dilation, it was possible to determine to what extent microvascular pressures at rest depend on the active control and passive hemodynamic characteristics of specific vascular segments. New Zealand White rabbit (2-3 kg body wt) had a mean arterial pressure of 70-75 mmHg. However, pressures in arterioles of both species became equivalent at the second order of arteriolar branching within the bowel wall, and pressures in the smallest mucosal venules were 13.7±0.6 (SE) mmHg in rabbits and 14.9±0.3 mmHg in rats. Maximum vasodilation to ~300% of the control blood flow increased mucosal venule pressures ~10 mmHg in rats compared with ~4 mmHg in rabbits. The increased mucosal venule pressure during vasodilation was primary due to increased pressures within the submucosal small arterioles, which immediately precede the villus vasculature in both species. The increased blood flow during vasodilation was due primarily to a decreased resistant of the small arteries and large arterioles, even though pressures in these larger vessels changed only ~10%. This situation allows a major decrease in intestinal vascular resistant to substantially increase blood flow with a minimal increase in mucosal microvascular pressures.
|Original language||English (US)|
|Journal||American Journal of Physiology - Gastrointestinal and Liver Physiology|
|State||Published - 1987|
ASJC Scopus subject areas
- Physiology (medical)