Effect of lysosomotropic agents on the taurocholate-stimulated biliary excretion of horseradish peroxidase

Marinelli, Raúl A.; Peñalva, Guillermo L.

doi:10.1016/0006-2952(92)90488-5

Cited by 7 publications

(2 citation statements)

References 19 publications

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“…A single i.v. dose of HRP (1.9-3.5 mg) [35], dissolved in 0.5 ml of saline, was injected over a 30-s interval through the femoral vein catheter. Bile was collected in preweighed vials at 5-min intervals for 40 min, and then every 10 min over the next 30 min.…”

Section: Biliary Excretion Of Hrpmentioning

confidence: 99%

Adaptive hepatic changes in mild stenosis of the common bile duct in the rat

et al. 1998

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Adaptive hepatic changes were investigated in rats with mild stenosis of the common bile duct and in sham-operated controls. The studies were performed 24 h and 7-12 days postoperatively. A continuous intravenous infusion of taurocholic acid at stepwise-increasing rates was performed to explore the responses to bile acid effects. During the infusion, bile flow and the outputs of bile acids, phospholipids, cholesterol, alkaline phosphatase and gamma glutamyl transpeptidase were studied. At the end of the infusion, hepatic morphometric measurements were performed. In other experimental sets, biliary excretions of horseradish peroxidase, a marker of microtubule-dependent vesicular transport in the hepatocyte, and sulphobromophthalein, a well-known organic anion model, were studied. In other rats, bile acid pool size and composition were determined by depletion of bile. The results in rats with mild stenosis maintained for 24 h showed a greater susceptibility to the toxicity of taurocholic acid, as revealed by the abrupt decrement in bile flow at high rates of infusion, and increased outputs of phospholipids and canalicular enzymes. Conversely, rats with mild stenosis maintained for 7-12 days showed decreased bile acid maximum secretory rate and biliary outputs of phospholipids and canalicular enzymes, as well as hepatocyte hypertrophy. These findings may explain the limited hepatic and systemic repercussion of experimental mild stenosis of the common bile duct and help us to understand the early stages of constriction of the common bile duct in man.

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Section: Biliary Excretion Of Hrpmentioning

confidence: 99%

Adaptive hepatic changes in mild stenosis of the common bile duct in the rat

et al. 1998

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“…This is supported by the electrophoretic analysis of the bile, which revealed that insoluble radioactivity was largely associated with 40-kDa protein, and by the similar kinetics and percentage of injected dose excreted in bile observed for TCA-precipitable radioactivity and HRP activity, which is known to be associated in bile only with intact protein (Lowe et al 1988). This HRP appearing intact in bile is expected to arrive entirely via the direct transcytotic pathway, since an appreciable lysosomal contribution may be excluded under normal conditions (Mori et al 1990;Marinelli and Peñalva 1992;Yamaguchi et al 1992). In line with it are the results indicating no major effect of chloroquine or leupeptin on the biliary output of TCAprecipitable radioactivity (see Fig.…”

Section: Discussionmentioning

confidence: 99%

Assessment of the in vivo hepatic lysosomal processing of horseradish peroxidase

Marinelli¹,

Pellegrino²,

Larocca³

1996

Can. J. Physiol. Pharmacol.

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The lysosomal processing of horseradish peroxidase (HRP) was assessed in this study, i.e., its lysosomal proteolysis and the biliary output of its possible lysosomal metabolites by rat liver in vivo. HRP was covalently linked to [14C]sucrose to provide a label that remains trapped within lysosomes after proteolysis. The [14C]sucrose-labelled HRP was injected into the portal vein of rat, and after 30 min about 34% of the injected radiolabel was present in the liver. Subcellular fractionation by differential centrifugation and further purification of lysosomes in a Percoll gradient showed that radiolabel was concentrated in lysosomes and indicated that about 91% of the total proteolysis of HRP in liver could be attributed to these organelles. The in vivo lysosomal degradation rate of HRP at 30 min was about 40%/h, decreasing over time. The lysosomal inhibitors chloroquine and leupeptin suppressed proteolysis of HRP by about 30 and 60%, respectively. Analysis of the 14C excreted in bile by trichloroacetic acid precipitation and by SDS-polyacrylamide gel electrophoresis showed a minor fraction, which was intact HRP (40 kDa), and a major fraction, which was associated with material smaller than 3 kDa. The biliary output of these low molecular mass products, in contrast to that of intact HRP, did not gradually decline with time and represented about 3% of the corresponding amounts in liver. Chloroquine and leupeptin specifically decreased their biliary excretion (about 60%), giving additional support to their lysosomal origin. In addition, the overall hepatic processing of [14C]sucrose-labelled HRP did not differ from that of the native HRP measured by enzyme assay, indicating no significant alteration caused by the labelling procedure.

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