Varying total tissue pressures and the concentration of initial lymphatic lymph

The concentration of protein in the initial lymphatics on the peritoneal surface of the diaphragms of mice was compared, by light microscopical photodensitometry, with that of the test solution introduced into the peritoneal cavity. Some diaphragms were studied, in vitro, at varying intervals (up to 30 min) after the initiation of a continuous contraction. There was an initial large increase in the concentration of the initial lymphatic lymph (at 10 sec), but this was less after 45 sec; it returned to equal that of the test solution by about 10 min, and then remained at this level. If the diaphragms were left in a relaxed state in an organ bath, the concentration of the lymph remained equal to that of the test solution. After this, the concentration again greatly increased 10 sec after a contraction was initiated, and was again somewhat less than this after 45 sec of contraction. If the test solution was left in the peritoneal cavity for 30 min, the intralymphatic concentration was once more considerably increased after 10 sec of contraction; it equalled the test solution if a 1-min relaxation was used in place of the contraction. These results imply that initial lymphatic lymph protein concentration should not be measured in immobilised tissue. They confirm that varying total tissue pressure is essential for the operation of the initial lymphatic force-pumps. Lack of motion may well cause increases in the measured tissue hydrostatic pressure (thus helping to explain differences between various techniques). This lack may well cause increases in the protein concentration of samples of interstitial tissue fluid.