The Effect of Muscle Activity on the Lymphatic and Venous Transport of Lactate Dehydrogenase

Abstract

Muscle activity (electrical stimulation of the muscles of the posterior extremity) in dogs with
thoracic duct fistula did lead to a fivefold increase of the LOH-activity in leg lymph. A
significant increase of enzyme activity was observed also in blood serum. It is concluded, that
the enzyme protein is transported from the tissues during muscle activity not exclusively by the
lymphatics but also by the veins.
The view, that protein molecules are transported from tissues to the blood stream
exclusively by the lymphatic vessels is more or less generally accepted (1, 4). It was
however shown that colloides injected into some tissues are to a considerable extent
absorbed also by the blood capillares (2, 8). The objection can nevertheless be raised,
that in these experiments the colloidal substances were actually driven by the injection
pressure through the damaged capillary wall into the vessel lumen.
The activity in blood plasma of the cytoplasmic enzyme lactate dehydrogenase is
markedly increased in various pathologic conditions. In these states the enzyme enters
into the circulation in consequence of cellular damage or increased membrane permeability.
Plasma LDH level is however raised also by hypoxia and muscular activity
(3, 6, 7, 11). There is no evidence for the damaging effect of muscular exercise to the
capillary wall. Accordingly, LDH leaking during muscle activity into the intercellular
fluid may be a suitable molecule for the study of protein transport from the tissues. LDH
has the further advantage that its source can be traced back to the tissue of origin by
separating electrophoreticaly the component isoenzymes. As it is well established, the
individual tissues show a specific isoenzyme pattern and in pathologic conditions the
enzyme from the damaged tissues does not only increase LDH activity in plasma but
also procedures a characteristic shift in the LDH-isoenzyme pattern (5, 13, 14, 16).
In the experiments to be reported the effect of muscular activity on lymphatic and
plasma enzyme activity and LDH-isoenzyme pattern was studied in dogs. Consequently
it could be shown that the enzyme protein is transported from the activity tissues by
lymphatic as well as by venous channels.