Alkaline phosphatase activity in lymph and serum of bile duct-ligated rats

To determine whether liver alkaline phosphatase (AP) reaches the circulation by crossing the space of Dissé and traversing lymphatic channels to the thoracic duct, AP was measured in lymph and serum hourly for 12 h after bile duct ligation in thoracic duct cannulated rats. AP did not rise at any time point in lymph, was markedly increased in serum by 7 h when compared with controls (p less than 0.05), and continued to rise for the next 5 h. However, AP in the thoracic duct lymph was increased 5-fold by corn oil feeding. Molecular weight for serum AP from bile duct-ligated rats was determined by gel chromatography and found to be approximately 125,000. Thus, hepatic AP molecules probably pass freely through the large openings in the sinusoidal endothelial lining and are transported out of the liver chiefly in sinusoidal blood, which flows more rapidly than liver lymph.