Exchange of Albumin Between Plasma and Lymph

Abstract

Human and canine serum albumin, labeled with I131 was injd. intraven. into dogs and observations were made on the exchange of the labeled albumin between plasma and lymph. The radioactive iodinated albumin mixes uniformly in the plasma within 3 to 5 min. and then disappears from the plasma according to a double exponential function. A faster component represents mixing into interstitial (and lymph) systems. It corresponds to an albumin transfer of approx. 0.1%/min. This is 10 times as fast (0.01%/min.) as the 2d phase which represents metabolic turnover of albumin. The radioactive iodinated albumin appears in thoracic duct lymph within 10 min. after its injn. and accrues steadily. At from 7 to 13 hrs., the specific activities of plasma and lymph become equal. Thereafter, the activity in plasma and lymph decrease in a parallel fashion. This represents the metabolic turnover. The plasma disappear-ance curve can be used to calculate the total amt. of interstitial fluid albumin as well as the plasma volume. The significance of the results is discussed and it is shown that lymph is not a direct product of plasma filtrate.