Dynamics of water and protein transport through and around the canine medial iliac lymph nodes

Although isolated popliteal node perfusion studies have shown intranodal exchange of water between blood and lymph, questions remain about the significance of such studies. Do some nodes exchange protein with blood, and are there shunt pathways around nodes which tend to buffer intranodal exchange of water? Finally, what is the magnitude of difference in using postnodal lymph to compute tissue capillary membrane parameters of reflection coefficient, sigma, and permeability-surface area product, PS? Seventeen conditioned dogs were randomly divided into matched experimental (N = 8) and sham (N = 9) groups in which lumbar trunk lymph was measured for flow (JV) and lymph/plasma protein concentration ratios (R) before and after ligation or sham ligation of the medial iliac lymph node (MILN). Ligation reduced (JV) from 25.89 +/- 4.21 SEM microliter . min-1 . kg-1 to 20.45 +/- 1.84 (P less than .008), decreased R from .66 +/- .04 to .55 +/- .02 (P less than .0000), increased sigma from .42 +/- .04 to .55 +/- .04 (P less than .004), and did not change PS which was 11.45 +/- 2.13 before and 14.43 +/- 4.19 after ligation. No similar changes occurred in the sham group. Of four hypotheses tested, the data were compatible only with post ligation flow equal to the sum of tissue lymph production and efferent flow from upstream nodes. Protein moved from blood into the nodal lymph nearly with the ease of water. Reflection coefficient was 23% higher at the afferent level than in the post nodal lymph, but PS was unaffected by the MILN. Differences in using post nodal sigma and PS to compute tissue fluid levels of protein are about 10% at these flow, and shunt flow is as high as 79% of lumbar trunk flow. Conclusions based upon sigma and PS differences across the node must be tempered because of the possibility of the trend toward lymph-blood equilibration of afferent lymph if it passed through several upstream nodes.