Effects of adenosine on intestinal hemodynamics, oxygen delivery, and capillary fluid exchange.

Systemic arterial pressure, superior mesenteric arterial and venous pressures, blood flow, arteriovenous oxygen difference, lymph flow, and intestinal volume were monitored continuously from an autoperfused loop of cat ileum to determine the effects of locally infused adenosine on intestinal hemodynamics, oxygen consumption, and capillary fluid exchange. The results indicate that adenosine, inosine, and hypoxanthine are vasodilators in the intestinal circulation. Local infusion of adenosine significantly reduces vascular resistance, but lymph flow, lymph oncotic pressure, and lymphatic protein flux remained unchanged from control, and the intestinal volume rapidly became constant after an initial blood volume shift. Intestinal oxygen consumption decreased significantly in both autoperfused and constant flow preparations. Pretreatment with aminophylline prevented the reduction in oxygen consumption and greatly attenuated the vasodilatory effect of adenosine. The reactive hyperemic response to 60-s arterial occlusions was virtually unchanged following aminophylline treatment. Adenosine depressed oxygen utilization of mucosal and muscularis strips in vitro and caused a significant redistribution of blood flow from the mucosal-submucosal layer to the muscularis in autoperfused preparations. The results of this study indicate that adenosine significantly reduces vascular resistance and oxygen consumption, yet does not alter fluid exchange in the small intestine.