Vasodilation of the normal and ischemic canine mesenteric circulation

This study was designed to assess the vasodilatory effects of intraarterial infusions of prostacyclin, prostaglandin D2, and an adenosine analog, 2-chloroadenosine, on the mesenteric circulation of the anesthetized dog during resting conditions and during digoxin-induced ischemia. Blood flow to a segment of intestine, arteriovenous oxygen content difference, and intramural blood flow distribution were measured, and calculations were made for oxygen consumption and fractional blood flow to the mucosal-submucosal and muscular compartments of the gut wall. In the normal circulation, prostacyclin increased blood flow, oxygen consumption, and fractional mucosal-submucosal flow. Before administration of digoxin, prostaglandin D2 also produced an increase of blood flow and oxygen consumption but caused a redistribution of blood flow from the mucosal-submucosal to the muscle layer, whereas 2-chloroadenosine produced effects similar to prostacyclin, i.e., an increase in blood flow and oxygen consumption, with an increase in the fraction of total blood flow perfusing the mucosa-submucosa. Digoxin administration produced a decrease in blood flow, oxygen consumption, and fractional flow to all layers of tissue. All three vasodilators reversed ischemia and hypoxia produced by digoxin. Prostacyclin and 2-chloroadenosine caused an increase in mucosal-submucosal blood flow during ischemia while prostaglandin D2 did not affect mucosal-submucosal flow and actually redistributed flow to the muscle layer. These data indicate that all three agents are potent vasodilators of the canine mesenteric circulation and all three reverse digoxininduced ischemia and hypoxia in this vascular bed. Prostacyclin and 2-chloroadenosine are selective mucosal dilators which would more probably induce hemodynamic and metabolic reversal of intestinal ischemie necrosis.