Project: Research project

Project Details


We continue to test the hypothesis that exocytosis of lysosomal contents
into biliary canaliculi is a major excretory route for hepatocyte
lysosomes. We propose to: (1) Relate biliary excretion of lysosomal
contents to turnover of lysosomal constituents by studying: a) turnover
rates of hepatic lysosomal enzymes relative to their biliary excretion; b)
amount of lysosomal enzymes released by isolated hepatocytes relative to
their cellular content; c) effects of alterations in hepatic autophagy and
heterophagy on biliary excretion of lysosomal enzymes. (2) Study
regulation of hepatic lysosomal enzyme activities by measuring activity and
content of lysosomal hydrolases by enzymatic assays and radioimmunoassays,
respectively. (3) Study hepatic handling of chole-cystokinin (CCK) and
renin, proteins that may be processed in hepatocyte lysosomes, by: a)
determining hepatic sites of cellular and subcellular metabolism of labeled
CCK peptides; b) purifying and labeling rat renal renin and studying
hepatic processing of labeled ligand. (4) Characterize the role of
hepatocyte lysosomes in biliary metal excretion using animal models of
hepatic iron and copper overload by assessing: a) effects of
lysosomotropic agents on biliary metal secretion; b) the form of iron and
copper in bile; c) metal-induced changes in hepatic lysosomal enzyme
content, lipid and protein composition of lysosomal membranes, and
appearance of pericanalicular lysosomes; d) the fate of biliary iron in the
intestine; and e) the effect on hepatic and biliary metal concentrations of
chronic administration of agents which accelerate release of lysosomal
contents into bile. (5) Explore the role of hepatocyte lysosomes in
lipoprotein processing and in biliary excretion of lipids and
apolipoproteins by: a) characterizing molecular forms of apolipoproteins
B, A-I and A-II in human bile; b) studying the relationship between biliary
lipid secretion and hepatic uptake of LDL; c) assessing binding to liver
plasma membranes of labeled LDL and HDL3 after bile acid administration;
and d) studying effects of lysosomotropic agents on biliary lipid
secretion. We will utilize intact rats and isolated livers, cells, and
organelles, and apply novel biochemical and morphologic techniques
(radioimmunoassays, immunocytochemistry). Our long-term objectives are to
define the physiological and biochemical bases for and the functional
significance of the release of lysosomal contents into bile, identify
disturbances of this pathway relevant to disease, and develop therapies
which accelerate biliary excretion of toxic materials that accumulate in
hepatocyte lysosomes.
Effective start/end date12/1/783/31/18


  • Medicine(all)