Protein Concentration and Colloid Osmotic Pressure of Rat Skeletal Muscle Interstitial Fluid

Abstract Protein concentration and colloid osmotic pressure (COP) were estimated in the fluid contained in nylon wicks after implantation in skeletal muscle of rats for 1 to 3 h. After 1 and 2 h implantation wick fluid showed an albumin/total protein ratio of 0.44, compared to 0.61 in plasma. Average concentrations relative to that of plasma were 0.37 for albumin, 0.52 for total protein, and 0.76 (calculated by difference) for non‐albumin protein. After 3 h implantation these ratios had increased significantly to 0.49, 0.69 and 1.07 respectively, presumably indicating beginning inflammation. The unexpected “excess” of non‐albumin wick fluid protein had an electrophoretic mobility like that of plasma β‐globulins, but its origin,‐from plasma or muscle‐is uncertain. Wick fluid COP averaged 8.7 mm Hg, as compared to a plasma COP of 18.9 mm Hg.