Ultrastructural evidence for the synthesis of serum amyloid A protein by murine hepatocytes

Abstract

After administration of an amyloid-inducing agent to mice, intracytoplasmic localization of serum amyloid A protein in hepatocytes was examined by immunoelectron microscopy. From 6 hours to 14 days after amyloidogenic stimulation, the reaction products were noted mainly on the microvilli and in a few cisternae of Golgi apparatuses. When colchicine was given 3 hours before sacrifice, the reaction products were located in round or oval structures presumed to be the secretory granules derived from the Golgi apparatus and in some autophagosomes. Kupffer cells contained the reaction products during the observation period of 12 hours to 14 days in the phagosomes and on the surface of microvilli or pseudopods but not in the organelles concerned with protein synthesis. These results conclusively support the idea that serum amyloid A protein is synthesized in hepatocytes and that colchicine inhibits the secretion of this protein from hepatocytes into serum.