Subcellular localization of B apoprotein of plasma lipoproteins in rat liver

Multispecific antigen-binding fragments (Fab) from rabbit antisera against rat very low density lipoproteins (VLDL) and Fab against rat low density lipoproteins that were monospecific for the B apoprotein were conjugated to horseradish peroxidase. Conjugates were incubated with 6-mum frozen sections from fresh and perfusion-fixed livers and with tissue chopper sections (40 mum thick) from perfusion-fixed livers. In the light microscope, specific reaction product was present in all hepatocytes of experimental sections as intense brown to black spots whose locations corresponded to the distribution of the Golgi apparatus: along the bile canaliculi, near the nuclei, and between the nuclei and bile canaliculi. Perfusion fixation with formaldehyde produced satisfactory ultrastructural preservation with retention of lipoprotein antigenic determinants. In the electron microscope, patches of cisternae and ribosomes of the rough endoplasmic reticulum (ER) and particularly its smooth-surfaced ends, vesicles located between the rough ER and the Golgi apparatus, the Golgi apparatus and its secretory vesicles and VLDL particles in the space of Disse all bore reaction product. The tubules and vesicles of typical hepatocyte smooth ER did not ...Continue Reading