WASHOUT OF PROTEIN IN DOG LUNG LYMPH

After an increase in microvascular filtration rate, lung lymph may con tain protein washed from the tissue spaces plus protein from the filtr ate. If so, then the lymphatic protein concentration may be significan tly higher than the filtrate protein concentration (C(f)). To test thi s hypothesis, we decreased the plasma protein concentration from 5.1 /- 0.6 to 0.54 +/- 0.15 g/dl and increased the pulmonary microvascular filtration rate in four dogs. We estimated C(f) to be 0.16 +/- 0.05 g /dl after we reduced the plasma protein concentration, and the lymphat ic protein concentration (0.43 +/- 0.04 g/dl) was significantly greate r than C(f). Our results indicate that lung microvascular membrane ref lection coefficients estimated from lung lymph data may be too low. Ho wever, the amount of error caused by tissue protein washout is probabl y small. To account for the protein washout error, we estimated the lu ng microvascular membrane reflection coefficient to be approximately 0 .74-0.76 instead of the approximately 0.70 previously reported for dog s (J. C. Gabel et al. J. Appl. Physiol. 55: 866-869, 1983).