The Contribution of Lymphatic Pathways during Recovery from Hemorrhage in the Toad Bufo marinus

Compensatory changes in blood volume following hemorrhage were studied in the toad Bufo marinus. Intact (n = 5), sham operated (n = 3), and animals with destroyed lymph hearts (LH-, n = 6) were bled to 78%, 78%, and 74% of their initial blood volumes, respectively. Post-hemorrhage changes in blood volume were estimated by analyzing changes in hematocrit and concentration of an injected plasma volume marker, Evans blue. Analysis of both markers indicated significant replacement of plasma volume following hemorrhage in the intact and sham animals. An acute compensation period lasting 10-25 min resulted in recovery to between 91% and 108% of initial blood volume. This replacement of plasma volume occurred without concomitant washout of an injected extracellular fluid (ECF) volume marker, SCN⁺. Therefore, the compensation resulted from redistribution of ECF rather than mobilization of intracellular fluid. Animals with destroyed lymph hearts showed no evidence of acute replacement. The animals in this group exhibited progressive hemoconcentration until death in 1-3 days. These results provide the first clear indication of the rapidity and extent of volume recovery in B. marinus. The absence of fluid replacement among the LH- animals suggests an important role for the intact lymphatic system in the response.