The endosomal compartment of rat hepatocytes. Its characterization in the course of [125I]insulin internalization |
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Authors: | A Robert J L Carpentier E Van Obberghen B Canivet P Gorden L Orci |
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Affiliation: | 1. Institute of Histology and Embryology, University of Geneva Medical School, Geneva, Switzerland;2. Institut National de la Santé et de la Recherche Médicale (INSERM U145) et Laboratoire de Médecine Expérimentale, Faculté de Médecine, 06034 Nice Cedex, France;3. National Institute of Arthritis, Diabetes, Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20205, USA |
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Abstract: | When freshly isolated hepatocytes are incubated with [125I]insulin in the presence of the microtubule-disrupting agent colchicine, internalization of the labelled hormone is not significantly altered. However, the drug limits the endocytosis of the labelled material to a peripheral band of cytoplasm extending 1 micron beyond the plasma membrane. Both in the presence and absence of colchicine, internalized [125I]insulin preferentially associates with clear vesicles (endosomes) and lysosome-like structures, but the relative amount of labelled material associated with clear vesicles is higher in the presence of the drug than in its absence. An inverse pattern is observed for the lysosome-like structures. As demonstrated by cytochemical methods, clear vesicles do not contain the lysosomal enzyme aryl sulfatase. Moreover, colchicine induces an increase of the clear vesicle diameter without affecting their frequency, while it perturbs multivesicular bodies and dense bodies in an opposite way by increasing their frequency without affecting their size. By reducing and/or delaying the fusion between internalized endocytotic vesicles and lysosomes, colchicine allows better characterization of the endosomal compartment of isolated rat hepatocytes and allows it to be distinguished from other compartments, such as multivesicular bodies and the Golgi apparatus. |
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Keywords: | To whom offprint requests should be sent. Address: Institute of Histology and Embryology CMU 1 rue Michel Servet CH-1211 Geneva 4 Switzerland. |
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