Characteristics of Reactive Hyperemia in the Canine Intestine

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Abstract
The isolated ileum of the dog shows a characteristic hyperemia following brief periods of arterial occlusion. The magnitude of this reactive hyperemia depends more upon prolongation of flow related to duration of ischemia, than upon increases of maximal or peak blood flow. Repayment of flow deficit, by the added flow of reactive hyperemia, averaged only 35% in the intestine, far below that found by others in skeletal muscle and in the coronary circulation. Nevertheless, estimates of oxygen debt indicated that this debt was overpaid, even after five minutes of ischemia. A small but consistent increase in weight of the isolated segment was observed during the postocclusion phase. It was found that this weight increase was due largely to increase of the volume of blood in the ileum. The peak of the volume increment appeared slightly later than the peak of flow increase, and for this reason was ascribed to increase in volume of the capacity vessels. In an attempt to assess the respective roles of myogenic vs. metabolic mechanisms in causation of reactive hyperemia, arterial pressure was restored during occlusion by injecting dextran solution into the arterial segment. Pressures in excess of control values did not abolish the hyperemic response. It was concluded that the reactive hyperemia observed in the ileum was chiefly metabolic in origin.

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