REGIONAL DIFFERENCES IN MICROVASCULAR RESPONSE IN RAT INTESTINE DURING ACUTE ELEVATION OF PORTAL PRESSURE

The effect of acute elevation of portal pressure on the blood flow of rat intestinal microvessels was studied using a laser Doppler velocime ter and in vivo microscopy. The total intestinal blood flow decreased when portal pressure increased more than + 15 cmH2O above the basal va lue. Blood flow in villus capillaries did not change at portal pressur es of + 5 to + 15 cmH2O, but did decrease at + 20 cmH2O. Blood flow in muscle capillaries decreased at atl steps of portal hypertension. Red blood cell velocity was decreased by portal hypertension in large ven ules, but not in small venules of the submucosa. Large venules, but no t small venules, dilated in acute portal hypertension. Large arteriole s in the submucosa constricted, while small arterioles dilated at port al preSSures of + 10 to + 15 cmH2O. In conclusion, the intestinal micr ovascular flow response differs according to the degree of portal hype rtension and the location on the microvascular tree. Blood flow in vil lus capillaries and in small submucosal venules is maintained at a sma ll degree of portal hypertension.