title: Receptor-mediated 125I-labelled insulin degradation in the rat hepatocyte. Studies using chloroquine.
abstract: Degradation of insulin during incubation with target cells occurs via receptor-mediated processes. In this study, receptor-mediated degradation of 125I-labelled insulin was investigated in rat hepatocytes, using the agent chloroquine. Chloroquine increased specific cell-associated 125I-labelled insulin at 37 degrees. The increased radioactivity with chloroquine was intracellular (53.3 +/- 1.2% of initially bound label was displaced by excess cold insulin; in control cells 67.0 +/- 2.1% was displaced, P less than 0.005). The effect of chloroquine was prevented by adding label at 15 degrees or by pre-treatment with 5 mM KCN, 5 mM NaN3 or 1 g/l bacitracin, which indicated a post-internalization site of action. Chloroquine had no effect on degradation of 125I-labelled insulin in buffer alone or in buffer previously incubated with cells. Specific studies of receptor-mediated degradation at 37 degrees showed that more 125I-labelled insulin remained associated with hepatocytes when chloroquine was present (P less than 0.0005 after 60 min). Analysis of chloroquine's effect on the intactness of 125I-labelled insulin released during processing of surface-bound label at 37 degrees showed that chloroquine-sensitive mechanisms accounted for at least 50% of receptor-mediated insulin degradation in rat hepatocytes.
mesh_terms: D000818:Animals; D001386:Azides / Q000494:pharmacology; D001414:Bacitracin / Q000494:pharmacology; D002738:Chloroquine / Q000494:pharmacology*; D007328:Insulin / Q000378:metabolism*; D008099:Liver / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D011190:Potassium Cyanide / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D011972:Receptor, Insulin / Q000378:metabolism*; D019810:Sodium Azide
chemical_list: D001386:Azides; D007328:Insulin; D001414:Bacitracin; D002738:Chloroquine; D019810:Sodium Azide; D011972:Receptor, Insulin; D011190:Potassium Cyanide