Origin and Composition of Hepatic Lymph Proteins in the Dog

Abstract

Pappenheimer (11) has shown that the walls of capillary vessels behaved as semipermeable
membranes. Applying this concept to the transcapillary transfer of macromolecules,
Grotte ( 4) and Mayer son et al. (8) measured the permeability of the dog's
capillaries by means of the plasma versus lymph concentration ratios of dextran molecules
of graded molecular size, after intravenous injection of the substance. Both workers
concluded that capillary walls contained two kinds of pores of different size. The molecular
sieve effect would be largely accounted for by a set of small pores having a radius
of about 40 A according to Grotte ( 4) or 110 A according to Mayer son et al. (8). The data
also required the assumption of the existence of larger pores, of undefined diameter, which
would allow free passage to particles of any molecular size up to a mo!. weight of 300 000.
It was also shown that each type of tissue had its own characteristic capillary permeability,
that of the liver being greater than that of the small bowel, and the latter in turn
exceeding the capillary permeability of the limbs or cervical region. Such differences
would arise both from regional variations in the distribution density of the pores and
from shifts in the ratio of large versus small pores, the pore sizes remaining constant.
The findings described above were all obtained by using dextran molecules, but in
theory they could equally well have been derived from a study of the plasma versus
lymph concentration ratio of endogenous plasma proteins. This presentation will be
concerned with an attempt in that direction, using as a model the plasma and hepatic
lymph of the dog.