Glucagon effect on intracellular proteolysis and pericanalicular location of hepatocyte lysosomes in isolated perfused guinea pig livers
| Autor: | Romana Lenzen, Peter Stark, Viktoria Kolb-Bachofen, Georg Strohmeyer |
|---|---|
| Rok vydání: | 1995 |
| Předmět: |
Male
Proteolysis Guinea Pigs In Vitro Techniques Biology Glucagon Lysosome medicine Animals Bile Tissue Distribution Secretion Amino Acids Hepatology medicine.diagnostic_test Bile Canaliculi Proteins Intracellular Membranes Perfusion Protein catabolism Secretory protein medicine.anatomical_structure Liver Biochemistry Hepatocyte Lysosomes Intracellular Peptide Hydrolases |
| Zdroj: | Hepatology. 21:1422-1428 |
| ISSN: | 1527-3350 0270-9139 |
| DOI: | 10.1002/hep.1840210528 |
| Popis: | In guinea pigs, glucagon choleresis is accompanied by a significant, but transient, stimulation of biliary protein secretion, which can be accounted for mainly by biliary discharge of lysosomal enzymes. To clarify whether intracellular proteolysis-a process regulated by glucagon and taking place predominantly in the lysosomes-may interact with biliary protein secretion, we determined hepatic proteolytic activity and bile secretory function during substrate deprivation, amino acid supplementation, and glucagon administration in isolated perfused guinea pig livers. To further elucidate the nature of transient lysosomal enzyme release into bile during glucagon infusion, we analyzed pericanalicular distribution of lysosomes by quantitative electron microscopy. The results demonstrate that intracellular proteolysis is accompanied by biliary excretion of lysosomal enzymes. Glucagon-induced secretion of these enzymes as well as labeled proteins into bile occurs independent of protein breakdown and cannot be modulated by addition of amino acids as potent inhibitors of intracellular proteolysis. During glucagon administration, bile canalicular area and pericanalicular distribution of secondary lysosomes show a rapid increase, which persists during the entire infusion period and thus does not explain the transient biliary release of lysosomal enzymes. We therefore postulate that regulation of this process must be located beyond the lysosomal compartment, either involving transport processes or intracellular kinetics of lysosome formation or altered fusion kinetics at the bile canalicular membrane compartment. Metabolic and biliary effects of glucagon seem to occur independent of each other and to underly different regulatory mechanisms. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|
Plný text