Labeled albumin in plasma and removal paths from pleural space in control and increased ventilation

Increased ventilation was shown to markedly increase lymphatic drainage and plasma content of labeled proteins injected into pleural space relative to control ventilation. These proteins reach plasma by lymphatic drainage: directly through parietal pleura stomata, and indirectly from pleural interstitium, reached by diffusion, convection and transcytosis. Increased drainage from interstitium should not involve a comparable increase in protein removal from pleural space by these transports, while increased drainage through stomata involves a comparable increase in protein removal. Hence, relative increase in labeled protein removal from pleural space caused by increased ventilation should be marked only if drainage through stomata contributed most of this removal, whereas relative increase of labeled proteins in plasma should be marked in either case. We injected 3 ml of albumin-Ringer with albumin-Texas red into the pleural space of three groups of anesthetized rabbits: control, CO2-, or muscle stimulation-increased ventilation. Increased ventilation for 3 h (78 and 61%, respectively) increased (P < 0.01) labeled albumin in plasma by 132 and 106%, respectively, but did not significantly increase its removal. Hence, lymphatic drainage through stomata should not contribute most of liquid and protein removal from pleural space.