Peritoneal lymphatic uptake of fibrinogen and erythrocytes in the rat

Intact and thoracic duct-cannulated rats were dialyzed at various intraperitoneal pressures with 5% bovine serum albumin solutions containing 125I-fibrinogen or 51Cr-erythrocytes. Lymphatic transport rates were calculated from the mass of tracer passing into the plasma space as function of tracer concentration in the peritoneal fluid during dialysis periods ranging between 143 and 360 min. Peritoneal protein concentrations were constant over the duration of the experiments. The calculated lymph flow rate was independent of intraperitoneal pressure and in intact rats averaged 2.85 +/- 1.22 microliters/min for uptake of 125I-fibrinogen and 2.60 +/- 1.17 for uptake of 51Cr-erythrocytes. However, the observed fluid loss rates from the peritoneal cavity were sensitive to the intraperitoneal pressure and were 5 to 20 times the calculated lymph flow rate. Mass balance experiments in two rats dialyzed with 125I-fibrinogen indicated that a significant proportion (28%) of tracer leaving the peritoneal cavity is absorbed by the anterior muscle wall of the abdomen and is probably trapped there because of its large molecular weight. Results from 125I-fibrinogen and 51Cr-erythrocyte uptake experiments both indicated that only approximately 30% of the total lymphatic drainage of the peritoneal cavity passes through the thoracic duct in rats.