ENZYMES IN TISSUE FLUID AND PERIPHERAL LYMPH

Abstract

Enzymes escaping from the tissue cells (e.g. LDH,

GOT, GPT) are present in the regional lymph often

in higher concentrations than in blood plasma. This

proves only the lymphatic transport of the enzyme

proteins but does not exclude the possibility of their

direct entry into the blood capillaries. In pathological

conditions e.g. after burning or tissue ischaemia

when the release of cellular enzymes is increased the

enzyme activities increase markedly in the regional

lymph but in many organs the direct entry of the

enzyme molecules into the blood stream is also

evidenced by a significant arterio-venous concentration

gradient. In some cases the venous transport

may be even much more important than the lymphatic

one.

The enzymes are released from the cells not into the

lymph but into the tissue fluid. It was shown that in

the subcutaneous tissue fluid enzyme concentrations

are normally higher than in the regional lymph. This

difference increases markedly after tissue injury.

Tissue fluid also contains more plasma protein than

lymph. Based on the above observations a two compartment

system of the tissue fluid has been proposed.

The first compartment is the pathway actually taken

by the fluid and protein leaving the blood capillaries

and entering into the lymphatics. The second compartment

is a pool not directly drained by the lymphatics

and it represents the true tissue fluid.