Down-regulation of insulin receptors in the heart: studies on primary cultured adult cardiac myocytes.
Primary cultured cardiac myocytes from adult rats have been used to study insulin receptor regulation. Culturing of cells in the presence of insulin induced a dose-dependent down-regulation of insulin binding with a maximal effect of 35% at an insulin concentration of 1.7 X 10(-7) mol/l. The number of high-affinity sites decreased from 110 000 to 70 000 sites per cell in control and down-regulated cells, respectively, with no change in the apparent affinity constant. Down-regulation was found to be rapid (t 1/2 = 3 h) and fully reversible. Culturing of cells in the presence of cycloheximide (0.1 mmol/l) or Tris (35 mmol/l) resulted in a further time-dependent increase in insulin-induced receptor loss with no effect on insulin binding to control cells. The action of both agents was found to be additive reaching a down-regulation of 51% after a culture period of 16 h. Recovery of insulin binding activity after removal of insulin remained unaffected in the presence of cycloheximide, whereas Tris inhibited this process by 74%. In conclusion our results show that the concept of insulin-induced receptor down regulation can be extended to the adult heart muscle. Moreover the data suggest involvement of protein synthesis and receptor recycling in this process.
D000818:Animals; D002478:Cells, Cultured; D003513:Cycloheximide / Q000494:pharmacology; D003864:Depression, Chemical; D007328:Insulin / Q000494:pharmacology*; D009124:Muscle Proteins / Q000096:biosynthesis; D009206:Myocardium / Q000378:metabolism*; D051381:Rats; D011972:Receptor, Insulin / Q000187:drug effects* / Q000378:metabolism; D014325:Tromethamine / Q000494:pharmacology
D007328:Insulin; D009124:Muscle Proteins; D014325:Tromethamine; D003513:Cycloheximide; D011972:Receptor, Insulin