Intestinal mucosal oxygenation influences absorptive hyperemia

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Abstract
Intestinal villus O2 tension (PO2) is decreased from normal values of 14-17 to 4-7 mmHg, and blood flow is nearly doubled during glucose absorption. The role of O2 supply to the mucosa in the absorptive hyperemia mechanism was evaluated. With a constant PO2 (40-45 mmHg) over the rat intestinal muscle layer, the mucosal tissue PO2 increased only 4-5 mmHg, and intestinal blood flow decreased from .apprx. 125 to 65% of control (PO2 = 40-45) as the mucosal solution PO2 increased from 5 to 75 mmHg. When glucose was present (100 mg/100 ml), mucosal tissue PO2 was 5-7 mmHg at mucosal suffusion PO2 of 5-75 mmHg. Blood flow in the presence of glucose was 210 and 110% of control at a solution PO2 of 5-10 and 70-75 mmHg. Tissue PO2 in the vicinity of the submucosal series arterioles was only slightly affected by all of the manipulations described. At rest or during glucose exposure, elevation of mucosal solution PO2 caused constriction, and lowering the mucosal solution PO2 caused dilation even though tissue PO2 in the various regions of the bowel wall remained nearly constant. The O2 supply available for the tissue rather than the actual tissue PO2 is best correlated to the O2 role in control of arterioles throughout the intestine during absorptive hyperemia.