Breakdown of exogenous insulin by langerhans islets of the pancreas in vitro |
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Authors: | K.-D. Kohnert H.-J. Hahn H. Zühlke S. Schmidt H. Fiedler |
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Affiliation: | Zentralinstitut für Diabetes “Gerhardt Katsch”, Bereich experimentelle Diabetesforschung, 2201 Karlsburg GDR |
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Abstract: | Pancreatic islets were isolated from Wistar rats, albino mice, spiny mice and sand rats (Psammomys obesus). Evidence is presented that pancreatic islets contain an enzyme system degrading insulin in the presence of glutathione or other sulfhydryl-containing compounds. Apparent Km values for insulin and glutathione (in the presence of EDTA) are 14.0 μM (mol. wt 5700) and 1.28 mM, respectively. Maximum breakdown of 125I-labeled insulin was found at about pH 7.2. After ultracentrifugation of islet homogenates the microsomal fraction contained the greatest relative specific insulin-degrading activity. The specific insulin-degrading actvitity was found to be higher in Wistar rats and albino mice than in spiny mice and sand rats. Starvation of Wistar rats for 72 h caused a decrease inthe enzymatic activity. |
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