Transcapillary Exchange of S35-Labeled 1-Methionine in the Human Forearm.

Abstract

In the forearm the maximum transcapillary loss of S35-labeled 1-methionine averaged 47.6 [plus or minus] 7.3%. Methionine exhibited a pattern of transcapillary net exchange which is consistent with intracellular binding. A high rate of net loss was observed for a much longer period than with thiocyanate ion and the equilibrium time was delayed considerably. Net return to the circulation was small compared to thiocyanate during the period of observation. On the basis of these and other observations it is suggested that 3 distinct classes of substances have characteristic patterns of transcapillary net exchange which may be distinguished with the present technique. These substances are (a) primarily extracellular ions, (b) primarily intracellular diffusible substances, and (c) highly diffusible molecules which are distributed throughout both compartments (body water).