Endocytosis of lactate dehydrogenase isoenzyme M4 in rats in vivo. Experiments with enzyme labelled with O-(4-diazo-3,5-di[125I]iodobenzoyl)sucrose

• Published in: Biochemical journal Vol. 202; no. 3; pp. 655 - 660
• Main Authors: De Jong, A S, Duursma, A M, Bouma, J M, Gruber, M, Brouwer, A, Knook, D L
• Format: Journal Article
• Language: English
• Published: England 15.03.1982
• Subjects: Animals; Autoradiography; Bone Marrow - enzymology; Carbon - pharmacology; Endocytosis - drug effects; Female; Half-Life; Iodobenzoates; Isoenzymes; L-Lactate Dehydrogenase - blood; L-Lactate Dehydrogenase - metabolism; Liver - cytology; Liver - enzymology; Male; Rats; Rats, Inbred BN; Rats, Inbred Strains; Tissue Distribution
• ISSN: 0264-6021; 1470-8728
• DOI: 10.1042/bj2020655

1. Pig lactate dehydrogenase isoenzyme M4 was labelled with O-(4-diazo-3,5-di[125I]iodobenzoyl)sucrose and injected intravenously into rats. Previous work has shown that this label does not influence the clearance of the enzyme (half-life about 26 min) and that it is retained within the lysosomes for several hours after endocytosis and breakdown of the protein [De Jong, Bouma & Gruber (1981) Biochem. J. 198, 45--51]. 2. The distribution of the radioactivity over a large number of tissues was determined 2 h after injection. A high percentage of the injected dose was found in liver (41%), spleen (10%) and bone including marrow (21%). 3. Autoradiography indicated uptake of the enzyme mainly by Kupffer cells of the liver, by spleen macrophages and by bone marrow macrophages. 4. Liver cells were isolated 1 h after injection of the enzyme. Kupffer cells, endothelial cells and parenchymal cells were found to endocytose the enzyme at rates corresponding to 4230, 35 and 25 ml of plasma/day per g of cell protein, respectively. 5. Previous injection of carbon particles greatly reduced the uptake of the enzyme by liver and spleen, but the uptake by bone marrow was not significantly changed.