TY - JOUR
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, Richard B.
AU - Barham, Steven S.
AU - Larusso, 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) expresed 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 liver 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) expresed 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 liver 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.
UR - http://www.scopus.com/inward/record.url?scp=0020505804&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0020505804&partnerID=8YFLogxK
U2 - 10.1016/S0016-5085(83)80083-3
DO - 10.1016/S0016-5085(83)80083-3
M3 - Article
C2 - 6413291
AN - SCOPUS:0020505804
SN - 0016-5085
VL - 85
SP - 1146
EP - 1153
JO - Gastroenterology
JF - Gastroenterology
IS - 5
ER -