Effects of Distension and Acetylcholine on Intestinal Blood Flow <i>in vivo</i>

Abstract

In vivo canine gut segments perfused by branches of the superior mesenteric artery were subjected to increased intraluminal pressure to observe the effects upon arterial inflow, measured with an electromagnetic blood flowmeter, and venous effluent collected by a cannula. Inflation of the intestinal segment with air simultaneously reduced both inflow and outflow. Intra-arterial infusion of acetylcholine increased blood flow, even with intraluminal pressure maintained at 40 mm Hg. Mechanical distension of the gut impedes blood flow, but this effect can be overridden by a vasodilator. These findings correspond to results observed in similar experiments on in vitro gut segments.

Effects of Motility and Luminal Distension on Dog Small Intestine Hemodynamics

“…The present study reconfirms the observations of several investigators showing that distension interferes with intestinal hemodynamics [1,3,6,7,[13][14][15][16]. While most of the authors reported hemodynamic impairments only for intraluminal pressures higher than 25-30 mm Hg, the present re sults show that an increase in vascular resistance is still observed for in traluminal pressures of near 10 mm Hg.…”

“…While most of the authors reported hemodynamic impairments only for intraluminal pressures higher than 25-30 mm Hg, the present re sults show that an increase in vascular resistance is still observed for in traluminal pressures of near 10 mm Hg. Moreover, the vascular respon ses lasted as long as the distension, without readjustment of the vascular resistance, as reported by several authors [3,7,13]. The experimental conditions were different in so far as the distension was performed by in jecting into the gut lumen a constant volume of liquid or gas, whereas in the present study the intraluminal pressure remained constant.…”

“…In the case of the intestine, this factor of a mechanical nature, is dependent either on the pressure in the gut lumen (distension) or on the activity of the muscular coats of this organ (motility). Numerous authors showed either by in vivo or in vitro studies that distension of the gut lu men affects mesenteric hemodynamics by increasing the vascular resist ance to blood flow [1,3,5,7,[13][14][15][16]. As far as the hemodynamic effects of spontaneous changes in motor activity of the small bowel are con cerned the data available so far remain conflicting.…”

Vascular Adjustments in Dilatory Reactions

“…On the other hand, under pre-and postganglionic stimulation after reserpinization, M a u sk o pf et al [1969] observed a-adrenergic blockade and application of guanethidine vasodilations with a successive escape on the vascular bed of the dog's skeletal muscle. Like other authors [D jo jo su g ito et al, 1968;Shehadeh et al, 1969;Brobman et al, 1970] they did not observe humoral cholinergic-induced escapes. The reason for this contrast to our results may lie in their insufficient doses of Ach, for the escape is strongly dose-dependent ( fig.…”

“…These results are in contrast to those of F o l k o w et al [1961] and D o r r and Brody [1965]. However, these authors did not find an escape reaction from vasodilation induced by in fusion of acetylcholine (Ach) in the vascular bed of skeletal muscle, nor did Shehadeh et al [1969] and Brobman et al [1970] do so in the intestinal circulation.…”