Protein concentration in interstitial and lymphatic fluids from the subcutaneous tissue.

The protein content of interstitial fluid and lymph from the same tissue was determined fluid samples of nanolitre volumes being taken from the subcutaneous tissue of rabbits by micropuncture. In the same area lymph was collected from lymphatic vessels of 30-100 mum. An electrophoretic technique in polyacrylamide gels in glass capillaries was used for the analysis of proteins. The gels were stained and then scanned on a microscope equipped with a moving table and photomultiplier. The area under each protein band was calculated from the recorded densitograms. The method required only a few nanolitres of fluid for analysis. Using solutions of known protein concentrations the relationship between the amount of protein and the area under the densitogram band was investigated. This relationship was found to be linear, making it possible to quantify the protein content of both interstitial fluid and lymph samples. The interstitial fluid/plasma concentration ratios for albumin, transferrin, globulins and total proteins were 0.42, 0.42, 0.32 and 0.37. The albumin/globulin ratio in interstitial fluid was found to be 1.60 of the plasma value although the values obtained for lymph were similar to those found for interstitial fluid. The similarity between the protein concentration of interstitial fluid and lymph indicated that the endothelial lining of the terminal lymphatics did not restrict the passage of macromolecules into the lymphatics.