Intestinal synthesis and lymphatic secretion of apolipoprotein A-IV after cessation of duodenal fat infusion: mediation by bile

We tested whether secretion of apolipoprotein (apo) A-IV depends upon intes tinal triglyceride (TG) transport by comparing output kinetics of TG and ap o A-IV during and after duodenal lipid infusion in lymph-fistula rats. Lipi d infusion (triolein. 40 mu mol/h, 8 h) produced increases in lymphatic TG and apo A-IV output. After 8 h, triolein infusate was replaced with glucose -saline; TG output returned to basal levels 4-5 h later. However, apo A-IV output continued at significantly elevated levels until 20 h after the star t of the experiment. Bile diversion blocked this continued output of A-IV d uring the post-lipid period, and resulted in basal TG output that was 75% l ower than in bile-intact rats. Return of bile or low-dose triolein infusion (5 mu mol/h) into the intestine reversed these effects, There were no diff erences in hepatic synthesis or filtration of plasma A-IV into lymph betwee n bile-intact and bile-diverted groups. Intestinal A-IV synthesis was eleva ted in both groups even during the post-lipid period. The results support t he hypothesis that intestinal triglyceride transport drives apo A-IV secret ion, and suggest the existence of a bile-dependent, post-translational mech anism for the control of lymphatic apo A-IV output. (C) 1999 Elsevier Scien ce B.V. All rights reserved.