Catalytic enzyme activity concentration in thoracic duct, liver, and intestinal lymph of the dog, the rabbit, the rat and the mouse. Approach to a quantitative diagnostic enzymology, II. Communication.

In the mixed body lymph of the thoracic duct and in the defined organ lymph of the liver and the intestine, the catalytic activity concentrations of up to sixteen enzymes and the concentrations of albumin and protein were determined, as well as the transport rate of these substances and their lymph/plasma ratio. Thoracic duct lymph specimens were obtained from an extracorporeal lymph shunt in anaesthetized and conscious dogs and from short-term fistulas in anaesthetized rabbits, rats and mice. Additionally, rabbits and rats underwent passive motion of the hind limbs in another experimental trial. Thoracic duct flow in anaesthetized dogs is only half that seen in conscious dogs, due to bypassed muscular lymph. A similar flow change is seen during passive motion of hind limbs in anaesthetized rabbits and rats. From a literature review of flow in the four main lymphatics of the body, it is concluded that the thoracic duct flow should account for 50-70% of total body lymph flow. In the anaesthetized state, flow is mainly of visceral origin. In the conscious state and during passive motion the increased flow is of muscular origin. In the latter case, the catalytic activities of enzymes like lactate dehydrogenase, malate dehydrogenase, creatine kinase, aldolase and phosphohexose isomerase, increase in lymph as does their lymph/plasma ratio. These enzymes have high catalytic activities in muscle. Their transport into the blood increases 2-3-fold, due to a doubling of lymph flow. Reported data for anaesthetized and immobile animals therefore far underestimate the significance of thoracic duct enzyme transport. Liver lymph was obtained from anaesthetized dogs and rabbits. Our finding that lymph catalytic activity for several enzymes is higher than in plasma is not compatible with the proposed delivery of plasma proteins directly into the sinusoidal space without prior mixing with the Space of Disse. Enzymes in liver lymph should derive from parenchymal and endothelial lining cells. Their site of delivery from the hepatocyte seems different from that of proteins. Liver lymph is an important transport route of enzymes into the blood. Intestinal lymph was sampled from anaesthetized dogs, rabbits and rats. It was shown that most enzymes from the intestine are primarily released into the interstitial space and from there are transported via the lymph into the blood.