Extrahepatic synthesis of lipoproteins of plasma and chyle: role of the intestine.

Several groups of investigators (1-3) have shown that the protein portion of the plasma lipo-proteins of the rat can be synthesized by the liver. The present studies were undertaken to determine whether any lipoprotein synthesis can occur in the absence of the liver. Previous work by Bragdon (4) and by Rodbell, Fredrickson, and Ono (5) has suggested intestinal synthesis of lipoproteins. Since their studies were carried out in intact animals, however, the liver could not be excluded as a source of these proteins. We have therefore meas-ured the synthesis of the protein component of the lipoproteins of chyle and plasma in hepatectomized dogs. Methods Male mongrel dogs weighing 12 to 18.5 kg were fasted for 18 hours before operation. The dogs were anesthe-tized with pentobarbital (35 mg per kg iv). The fol-lowing types of preparations were used: a) hepatecto-mized dogs, b) hepatectomized dogs with thoracic duct fistulas, c) eviscerated dogs, and d) an anesthetized nor-mal control. A one-stage hepatectomy was performed (6) in which a portacaval shunt was established and the liver re-moved after it had been stripped from the intrahepatic vena cava, which was left in situ. In the dogs in which the thoracic duct was cannulated, 50 to 100 ml of cream was fed 2 hours before the administration of anesthesia. A polyethylene tube was inserted into the thoracic duct in the neck, and the lymph was collected continuously; hepatectomy was then performed. In animals on which abdominal evisceration was performed, the stomach, in-