Effect of chloroquine on the form and function of hepatocyte lysosomes. Morphologic modifications and physiologic alterations related to the biliary excretion of lipids and proteins

R. B. Sewell, S. S. Barham, Nicholas F La Russo

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Abstract

In these experiments, we tested the hypothesis that chloroquine, a lysosomotropic agent which modifies protein and lipid metabolism by hepatocyte lysosomes, would alter the biliary excretion of lipids and lysosomal enzymes. We treated male rats for 5 days with intraperitoneal chloroquine (50 mg/kg body wt, n = 9) or saline (n = 8) and collected bile for 6 h via bile fistulas; rats were then killed and livers homogenized for biochemical analyses or processed for electron microscopy. Chloroquine markedly increased the biliary excretion of three lysosomal enzymes (mean ± SEM) expressed as milliunits of activity per gram liver: N-acetyl-β-glucosaminidase (24.4 ± 2.7 vs. 12.5 ± 1.4, p < 0.01), β-glucuronidase (26.4 ± 4.7 vs. 10.9 ± 1.4, p < 0.01), and β-galactosidase (9.8 ± 1.7 vs. 5.5 ± 0.8, p < 0.05). In contrast, biliary outputs of enzymes associated with other organelles (e.g., alkaline phosphodiesterase I and lactic dehydrogenase) were unaffected by chloroquine treatment. Biliary cholesterol secretion was decreased after chloroquine administration (0.28 ± 0.02 μmol/g vs. 0.39 ± 0.03 μmol/g liver, p < 0.01), but bile acid and phospholipid secretion were not altered; as a result, cholesterol saturation of bile decreased by 22% (p < 0.05). Hepatic activities of all three lysosomal enzymes were increased after chloroquine administration (p < 0.04); activities of enzymes associated with mitochondria, plasma membrane, endoplasmic reticulum, and cell sap were not altered. Morphometric analysis of electron micrographs of rat livers demonstrated a marked increase (p < 0.001) in the number of lysosomelike vesicles and autophagic vacuoles in the vicinity of bile canaliculi after chloroquine administration; also, the number of canalicular microvilli decreased (p < 0.003) after chloroquine treatment. We conclude that altered hepatic lysosomal morphology and function after chloroquine is accompanied by marked changes in outputs of lipids and lysosomal enzymes into bile. These findings call attention to a possible role for hepatic lysosomes in modulating biliary protein and lipid secretion.

Original languageEnglish (US)
Pages (from-to)1146-1153
Number of pages8
JournalGastroenterology
Volume85
Issue number5
StatePublished - 1983

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Chloroquine
Lysosomes
Hepatocytes
Lipids
Liver
Bile
Proteins
Enzymes
Cholesterol
Phosphodiesterase I
Bile Canaliculi
Galactosidases
Hepatobiliary Elimination
Hexosaminidases
Glucuronidase
Microvilli
Vacuoles
Bile Acids and Salts
Lipid Metabolism
Endoplasmic Reticulum

ASJC Scopus subject areas

  • Gastroenterology

Cite this

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title = "Effect of chloroquine on the form and function of hepatocyte lysosomes. Morphologic modifications and physiologic alterations related to the biliary excretion of lipids and proteins",
abstract = "In these experiments, we tested the hypothesis that chloroquine, a lysosomotropic agent which modifies protein and lipid metabolism by hepatocyte lysosomes, would alter the biliary excretion of lipids and lysosomal enzymes. We treated male rats for 5 days with intraperitoneal chloroquine (50 mg/kg body wt, n = 9) or saline (n = 8) and collected bile for 6 h via bile fistulas; rats were then killed and livers homogenized for biochemical analyses or processed for electron microscopy. Chloroquine markedly increased the biliary excretion of three lysosomal enzymes (mean ± SEM) expressed as milliunits of activity per gram liver: N-acetyl-β-glucosaminidase (24.4 ± 2.7 vs. 12.5 ± 1.4, p < 0.01), β-glucuronidase (26.4 ± 4.7 vs. 10.9 ± 1.4, p < 0.01), and β-galactosidase (9.8 ± 1.7 vs. 5.5 ± 0.8, p < 0.05). In contrast, biliary outputs of enzymes associated with other organelles (e.g., alkaline phosphodiesterase I and lactic dehydrogenase) were unaffected by chloroquine treatment. Biliary cholesterol secretion was decreased after chloroquine administration (0.28 ± 0.02 μmol/g vs. 0.39 ± 0.03 μmol/g liver, p < 0.01), but bile acid and phospholipid secretion were not altered; as a result, cholesterol saturation of bile decreased by 22{\%} (p < 0.05). Hepatic activities of all three lysosomal enzymes were increased after chloroquine administration (p < 0.04); activities of enzymes associated with mitochondria, plasma membrane, endoplasmic reticulum, and cell sap were not altered. Morphometric analysis of electron micrographs of rat livers demonstrated a marked increase (p < 0.001) in the number of lysosomelike vesicles and autophagic vacuoles in the vicinity of bile canaliculi after chloroquine administration; also, the number of canalicular microvilli decreased (p < 0.003) after chloroquine treatment. We conclude that altered hepatic lysosomal morphology and function after chloroquine is accompanied by marked changes in outputs of lipids and lysosomal enzymes into bile. These findings call attention to a possible role for hepatic lysosomes in modulating biliary protein and lipid secretion.",
author = "Sewell, {R. B.} and Barham, {S. S.} and {La Russo}, {Nicholas F}",
year = "1983",
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T1 - Effect of chloroquine on the form and function of hepatocyte lysosomes. Morphologic modifications and physiologic alterations related to the biliary excretion of lipids and proteins

AU - Sewell, R. B.

AU - Barham, S. S.

AU - La Russo, Nicholas F

PY - 1983

Y1 - 1983

N2 - In these experiments, we tested the hypothesis that chloroquine, a lysosomotropic agent which modifies protein and lipid metabolism by hepatocyte lysosomes, would alter the biliary excretion of lipids and lysosomal enzymes. We treated male rats for 5 days with intraperitoneal chloroquine (50 mg/kg body wt, n = 9) or saline (n = 8) and collected bile for 6 h via bile fistulas; rats were then killed and livers homogenized for biochemical analyses or processed for electron microscopy. Chloroquine markedly increased the biliary excretion of three lysosomal enzymes (mean ± SEM) expressed as milliunits of activity per gram liver: N-acetyl-β-glucosaminidase (24.4 ± 2.7 vs. 12.5 ± 1.4, p < 0.01), β-glucuronidase (26.4 ± 4.7 vs. 10.9 ± 1.4, p < 0.01), and β-galactosidase (9.8 ± 1.7 vs. 5.5 ± 0.8, p < 0.05). In contrast, biliary outputs of enzymes associated with other organelles (e.g., alkaline phosphodiesterase I and lactic dehydrogenase) were unaffected by chloroquine treatment. Biliary cholesterol secretion was decreased after chloroquine administration (0.28 ± 0.02 μmol/g vs. 0.39 ± 0.03 μmol/g liver, p < 0.01), but bile acid and phospholipid secretion were not altered; as a result, cholesterol saturation of bile decreased by 22% (p < 0.05). Hepatic activities of all three lysosomal enzymes were increased after chloroquine administration (p < 0.04); activities of enzymes associated with mitochondria, plasma membrane, endoplasmic reticulum, and cell sap were not altered. Morphometric analysis of electron micrographs of rat livers demonstrated a marked increase (p < 0.001) in the number of lysosomelike vesicles and autophagic vacuoles in the vicinity of bile canaliculi after chloroquine administration; also, the number of canalicular microvilli decreased (p < 0.003) after chloroquine treatment. We conclude that altered hepatic lysosomal morphology and function after chloroquine is accompanied by marked changes in outputs of lipids and lysosomal enzymes into bile. These findings call attention to a possible role for hepatic lysosomes in modulating biliary protein and lipid secretion.

AB - In these experiments, we tested the hypothesis that chloroquine, a lysosomotropic agent which modifies protein and lipid metabolism by hepatocyte lysosomes, would alter the biliary excretion of lipids and lysosomal enzymes. We treated male rats for 5 days with intraperitoneal chloroquine (50 mg/kg body wt, n = 9) or saline (n = 8) and collected bile for 6 h via bile fistulas; rats were then killed and livers homogenized for biochemical analyses or processed for electron microscopy. Chloroquine markedly increased the biliary excretion of three lysosomal enzymes (mean ± SEM) expressed as milliunits of activity per gram liver: N-acetyl-β-glucosaminidase (24.4 ± 2.7 vs. 12.5 ± 1.4, p < 0.01), β-glucuronidase (26.4 ± 4.7 vs. 10.9 ± 1.4, p < 0.01), and β-galactosidase (9.8 ± 1.7 vs. 5.5 ± 0.8, p < 0.05). In contrast, biliary outputs of enzymes associated with other organelles (e.g., alkaline phosphodiesterase I and lactic dehydrogenase) were unaffected by chloroquine treatment. Biliary cholesterol secretion was decreased after chloroquine administration (0.28 ± 0.02 μmol/g vs. 0.39 ± 0.03 μmol/g liver, p < 0.01), but bile acid and phospholipid secretion were not altered; as a result, cholesterol saturation of bile decreased by 22% (p < 0.05). Hepatic activities of all three lysosomal enzymes were increased after chloroquine administration (p < 0.04); activities of enzymes associated with mitochondria, plasma membrane, endoplasmic reticulum, and cell sap were not altered. Morphometric analysis of electron micrographs of rat livers demonstrated a marked increase (p < 0.001) in the number of lysosomelike vesicles and autophagic vacuoles in the vicinity of bile canaliculi after chloroquine administration; also, the number of canalicular microvilli decreased (p < 0.003) after chloroquine treatment. We conclude that altered hepatic lysosomal morphology and function after chloroquine is accompanied by marked changes in outputs of lipids and lysosomal enzymes into bile. These findings call attention to a possible role for hepatic lysosomes in modulating biliary protein and lipid secretion.

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