AJP - Heart and Circulatory Physiology, Vol 243, Issue 3 351-H359, Copyright © 1982 by American Physiological Society
Quantitation of changes in lymph protein concentration during lymph node transit
T. H. Adair, D. S. Moffatt, A. W. Paulsen and A. C. Guyton
Many investigators assume the protein concentration and colloid osmotic
pressure of interstitial fluid and lymph to be identical even after the
lymph has passed through a lymph node. We quantitated the degree of
modification of lymph by the dog popliteal lymph node by perfusing isolated
lymph nodes in situ at physiological flow rates with homologous plasma or
plasma diluted to low protein concentration. This enabled us to compare
directly prenodal and postnodal lymph flows and protein concentrations.
When undiluted plasma was infused into the node, fluid filtered from the
blood into the lymph, diluting the lymph. When diluted plasma was infused,
fluid was absorbed from the lymph, concentrating the lymph. Nearly all
(98%) of the change in lymph protein concentration could be explained by
transfer of protein-free fluid either into or out of the lymph. However,
when the nodes were perfused with lymph having a colloid osmotic pressure
that exactly balanced the hydrostatic and osmotic forces acting across the
lymph node blood-lymph barrier, the lymph was not modified during nodal
transit. This "equilibrium colloid osmotic pressure" averaged 60% of that
of plasma. The concentrating-diluting mechanism became more significant as
the perfusion rate decreased and/or as the colloid osmotic pressure of the
afferent lymph was made progressively greater than or less than the
equilibrium colloid osmotic pressure. We conclude that lymph nodes modify
lymph protein concentration and colloid osmotic pressure except when these
are already at equilibrium values for given lymph node conditions.
Therefore, the assumption that postnodal lymph is representative of
interstitial fluid, especially at low but still physiological lymph flows,
is likely to be incorrect.
