Inhibition of down regulation by chloroquine in cultured lymphocytes (RPMI-1788 line).
We studied the effect of chronic exposure to insulin on insulin receptors of cultured lymphocytes (RPMI-1788 line). The cells treated with insulin (2 micrograms/ml) at 37 degrees C for 12 h, showed a 36.5% decrease in the number of binding sites. Solubilized extract from the cells treated with insulin showed a 35.9% decrease of binding capacity, suggesting that insulin exposure induced the loss of total (cell surface and intracellular) receptors. Insulin-induced loss of receptors was blocked by chloroquine, suggesting that receptor loss is mediated by a chloroquine sensitive pathway. Bacitracin, which inhibited the insulin degradation, had no effect on insulin-induced receptor loss in this cell line. We also found that vitamin K5, one of the insulin mimickers, induced a 31.5% loss of insulin receptors. Therefore, the post-receptor process appeared to mediate down regulation. In cultured lymphocytes, insulin exposure caused a significant loss of total receptors, suggesting that insulin-induced receptor loss may be due to receptor degradation. Insulin-induced receptor loss is mediated by a chloroquine sensitive pathway, and is related to the post-binding process stimulated by vitamin K5.
D001414:Bacitracin / Q000494:pharmacology; D002021:Buffers; D002460:Cell Line; D002738:Chloroquine / Q000494:pharmacology*; D006801:Humans; D007328:Insulin / Q000378:metabolism / Q000494:pharmacology*; D008214:Lymphocytes / Q000378:metabolism*; D011972:Receptor, Insulin / Q000187:drug effects / Q000378:metabolism*; D014812:Vitamin K / Q000031:analogs & derivatives / Q000494:pharmacology; D024483:Vitamin K 3 / Q000031:analogs & derivatives*
D002021:Buffers; D007328:Insulin; D014812:Vitamin K; D001414:Bacitracin; D024483:Vitamin K 3; D002738:Chloroquine; D011972:Receptor, Insulin; C024534:vitamin k5