INTRA- AND EXTRAVASCULAR DISTRIBUTION OF ALBUMIN AND IMMUNOGLOBULIN IN MAN

Abstract

The plasma proteins are constantly shuttling between

intravascular and extravascular spaces until catabolism.

The intravascular mass of a specific plasma protein is

determined by its individual rate of synthesis and the

mean total time it spends in plasma. The ratio of

intravascular to total mass (distribution ratio) is de-

termined by the relative rate, at which it passes from

plasma to interstitial spaces (transcapillary escape

rate: TER) and the relative return rate via lymph.

TER in a specific organ depends on the local leakiness

of the microvasculature. The overall value in normal

man varies with the molecular weight of the protein

being about 5%/h of the intravascular albumin mass,

3%/h for lgG and less than 1 %/h for lgM. The higher

the TER, the lower is the intravascular fraction.

Hypertension, diabetes mellitus, bums, myxedema

and certain types of liver cirrhosis will increase TER.

In hypertension and diabetes this may be compensated

for by an increased lymphatic return rate. Hypo-

proteinemia due to malnutrition or urinary or

gastrointestinal loss is accompanied by a shift from

the extravascular to the intravascular space.