The overall goal of this application is to evaluate the factors which affect lymph flow from the intestines and liver. Lymph vessels normally function to remove excess fluid from the tissues and transport the fluid to veins in the neck. Edema can develop only if the rate at which fluid enters a tissue exceeds the lymphatic flow rate. In edema, lymph flow is usually increased, and the increased flow may be caused by 1) an increase in the pressure driving lymph flow and/or 2) a decrease in the resistance through which the lymph must flow. The relative contributions of these two mechanisms deteritiine the lymphatic response in edema. Furthermore the lymphatic resistances and pressures determine the volume flow rate of the lymph and they determine the conditions under which lymph will flow. Unfortunately it is not possible to directly measure the resistance or driving pressure of lymphatic vessels. However it is possible to estimate the driving pressures and resistances from flow vs. pressure relationships of cannulated lymphatics. Accordingly, the first two specific aims are to analyze the intestinal and liver lymphatic systems of sheep in terms of the flow vs pressure relationships of cannulated lymphatic vessels. Lymphatic vessels from both organs will be analyzed under control conditions and during an increase in lymphatic flow. The third specific aim is to test the hypothesis that increases in liver lymph flow will slow the flow of intestinal lymph. Because both liver and the intestinal lymph drain through the thoracic duct, an increase in the flow from the liver could interfere with intestinal lymph flow. This will be tested by estimating the intestinal lymphatic flow under control conditions and during an increase in liver lymph flow. The results of all these studies should provide important information about 1) the mechanisms by which intestinal and liver lymph flow may increase and 2) the factors which limit lymph flow from the intestines and liver.
