Role of a lymphatic system in glucose absorption and the accompanying microvascular hyperemia

In this study we evaluated the importance of a functional intestinal lymphatic system on changes in arteriolar and venular blood oxygen content, vasodilation, and elevation of venous blood osmolarity during glucose absorption. Glucose absorption was associated with a doubling of the arteriovenous oxygen difference [(A-V)O2], a 50 mosM increase in venous blood osmolarity, and 17% dilation of the intermediate-diameter arterioles. After the lymph vessels were mechanically blocked with mineral oil, glucose absorption again doubled the (A-V)O2, indicating that glucose was absorbed without a functional lymphatic system. Furthermore, venous blood osmolarity and arteriolar diameter increased similarly with and without a functional lymphatic system. This study indicates that even though the lymphatic system likely facilitates distribution of hypertonic material in the bowel wall during absorption, blockade of the lymphatics did not appreciably hinder vasodilation, glucose absorption, changes in intravascular oxygen content, or the elevation of tissue hyperosmolarity, as judged by the tonicity of the venular blood. Therefore, passage of materials absorbed or released in the mucosa to the submucosa through venular blood flow may be very important to the mechanism of absorptive hyperemia.