Influence of venous congestion on blood-lymph transport of fluid and large molecules in the heat-injured dog's paw.

Hind paws of anesthetized dogs were exposed to moderate continuous heat (45--52 degrees C). Lymph flow (L) was increased to 5.61 (SD 3.26) times control levels, lymph:plasma concentration ratios for total plasma protein (RT) were increased to 3.23 (SD 1.33), and for exogenous Dextran-110 (RD) to 8.41 (SD 4.00) times control levels. Selectivity of the blood-lymph barrier for individual plasma proteins was also decreased. Elevation of venous pressure during heating resulted in an increase of L in 5 out of 8 experiments, with no consistent change in RT or RD. Increased protein flux was thus closely coupled to increased volume flow. These observations are consistent with the presence and persistence of intercellular openings or gaps in the microvascular endothelium.