Relationship of blood flow to pressure in the intestinal vascular bed of the dog

The relationship of pressure in the superior mesenteric artery, mesenteric small artery, mesenteric small vein, and portal vein to the rate of blood flow in the superior mesenteric artery was studied in eight dogs. Total bed resistance to blood flow decreased as a function of flow over the range 20–60 ml/min but increased as a function of flow over the range 90–270 ml/min. The onset and cessation of the resistance increase were associated with pressures in the superior mesenteric artery of 64 and 205 mm Hg, respectively. These resistance changes resulted mainly from change of resistance to flow through vessels less than 0.5 mm diameter. The findings suggest that the intestinal vascular bed, like the renal vascular bed, has a local mechanism which antagonizes changes of flow rate produced by variation of arterial pressure.