Characterization and regulation of insulin binding by embryonic chick heart cells.
We have compared insulin binding by heart cells at 7 and 14 days of development. Species specificity, optimum pH, temperature relationships, and time to equilibrium for binding of insulin were the same in both 7 and 14-day systems. Curvilinear Scatchard plots for chicken insulin binding were demonstrated. Binding affinities and capacities were calculated based on a two-receptor model including a specific high-affinity receptor and a less specific low-affinity receptor that bound insulin and other growth peptides. Apparent association constants (K(A)) were 4.0 and 0.05 nM(-1) and binding capacities were 600 and 9000 sites per cell for high- and low affinity receptors, respectively. We have also investigated the ability of insulin to regulate binding to its own receptors. Chick heart cells from 7- and 14-day embryos, cultured for 44 hr in insulin-enriched medium (3.4 microM), bound 50% less insulin (down-regulated) than control cells. At both developmental stages, down regulation was primarily a reduction in binding to the high-affinity receptor. The low-affinity receptor was less susceptible to down regulation and retained its ability to mediate maximal insulin stimulation of amino acid transport.
Serravezza
J C
JC
Division of Medical Genetics and Department of Pediatrics, Emory University School of Medicine, Atlanta, Georgia 30322, USA.
Wheeler
F B
FB
DeHaan
R L
RL
Elsas
L J
LJ
D000818:Animals; D001692:Biological Transport; D002642:Chick Embryo; D006321:Heart / Q000196:embryology*; D007328:Insulin / Q000378:metabolism*; D007700:Kinetics; D009206:Myocardium / Q000378:metabolism*; D011972:Receptor, Insulin / Q000378:metabolism; D015091:beta-Alanine / Q000031:analogs & derivatives / Q000378:metabolism
D007328:Insulin; D015091:beta-Alanine; C012924:2,2-dimethyl-beta-alanine; D011972:Receptor, Insulin