Measurement of microvascular transport parameters of macromolecules in tissues and organs of intact animals.

A critical analysis is presented of two widely used approaches to measurement of microvascular transport of large molecules in intact animals: (1) measurement of lymph flow and macromolecular solute concentration relative to plasma, and (2) tissue accumulation of tracer macromolecules. To demonstrate the advantages and limitations of each method, experimental results which permit direct comparison of the two methodologies are reviewed and analyzed, and sources of error in each pointed out. It is concluded that both approaches are valid under the appropriate conditions: steady state of lymph, initial transient state for tissue uptake. These conditions are mutually exclusive, but complementary. When the requirements for neither lymph collection or tissue accumulation alone can be satisfied experimentally, a combination of the two approaches can yield valid results.