For nearly a century lymph has been used to estimate the composition of tissue fluid. For this reason, many concepts in the field of lung liquid balance, capillary permeability, and tissue fluid dynamics are based on the assumption that tissue fluid and lymph are identical fluids. Although all of the lymph vessels have the potential to alter lymph, most investigators seem to agree that significant modification is most likely to occur within the lymph nodes. Recent studies have indicated that the lymph node functions as a fluid exchange chamber in which protein-free fluid is transferred between the blood and lymph compartments in a direction required to establish equilibrium of the osmotic and hydrostatic pressure acting across the lymph node blood-lymph barrier. Thus, a Starling force disequilibrium across this barrier causes the lymph proteins to become concentrated or diluted, depending on the direction of transfer of protein-free fluid through the barrier. However, when the Starling forces are balanced perfectly, the lymph is not modified. The experimental studies outlined in this proposal will be directed toward determining quantitatively the effect of lymph nodes on the composition of lymph and also quantitating lymph node Starling forces during various physiological states. Because an important issue in the field of lung liquid balance is the possibility of sheep caudal mediastinal modification of pulmonary lymph, the caudal mediastinal node, especially will be autoperfused with lung lymph having various protein concentrations, and prenodal and postnodal pulmonary lymph will be collected simultaneously for direct comparison of lymph proteins. Because the modification of lymph by lymph nodes is a function of imbalances in Starling forces acting across the blood-lymph barrier, the quantitative relationships among lymph node blood flow, isovolumetric filtration coefficient, and capillary pressure will be determined during normal conditions, and following both increases and decreases in blood flow. The quantitative data from these studies will be used in a system analysis of lymph node fluid dynamics, and this will make it possible to predict mathematically the effect of lymph nodes on the composition of lymph during a variety of physiological states. Finally, the long-term goal of this study is to use models of lymph node function in conjunction with models of tissue fluid dynamics to understand better the mechanisms of edema formation and other important concepts associated with fluid equilibria at the capillary level.
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| Adair, T H; Guyton, A C (1985) Modification of lymph by lymph nodes. III. Effect of increased lymph hydrostatic pressure. Am J Physiol 249:H777-82 |
| Adair, T H (1985) Studies of lymph modification by lymph nodes. Microcirc Endothelium Lymphatics 2:251-69 |
