A Quantitative Analysis of Hepatic Ultrastructure in Rats During Enhanced Bile Secretion

The ultrastructural changes in hepatocytes of rats subjected to selective biliary obstruction (SBO), wherein the biliary system draining approximately two-thirds of the liver is obstructed, were evaluated by quantitative electron microscopy or stereology. The remaining unobstructed portion of the organ compensates for this loss of bile secretion by functioning in a hypersecretory mode. This animal model permits the comparison of hepatocellular fine structure associated with the conditions of nonsecretion and hypersecretion of bile with that found in normal secreting sham-operated rats. Since recent evidence suggests the presence of lobular gradients in hepatic structure and function, both centrolobular and periportal hepatocytes were examined. The low incidence of Golgi membrane profiles in high magnification electron micrographs results in a low confidence level of sampling and, thus, necessitates the application of a novel parameter for estimating the amount of Golgi complex, i.e., the Golgi-rich area. For the most part, the lobular variation in hepatic fine structure in the sham-operated animals was similar to that described by Loud ('68). However, the periportal parenchyma contained approximately twice the volume of Golgi-rich area as the centrolobular tissue. The amount of cytoplasmic lipid increased significantly in the SBO unobstructed lobes, although there were few or no changes in the other intracellular organelles or inclusions except those related to the Golgi complex. The volume of Golgi-rich area increased significantly in the centrolobular tissue of the SBO unobstructed (hypersecretory) lobes to the extent that both intralobular zones contained similar amounts of this component. These data suggest that the Golgi complex is a dynamic unit which responds to changes in hepatocellular activity and may be involved in bile secretion.