Binding, internalization, and degradation of 125i-multipotential colony-stimulating factor (interleukin-3) by FDCP-1 cells

Abstract

The kinetic parameters involved in determining the steady-state interaction of Multi-CSF with FDCP-1 cells at 37°C have been determined by kinetic analysis under steady-state conditions and by curve-fitting the rate of approach to steady-state conditions. The two methods are in substantial agreement and yield values of Vr=28 receptors/cell/min for the rate of appearance of receptors at the cell surface, ke and ki =0.061 min-1 and 0.0044 min-1 for the rate constants of internalization of occupied and unoccupied receptors, respectively, kh =0.008 min-1 for the rate constant of degradation of internalized ligand, ka =2.9×108 M-1 min-1 for the rate constant of association and kd =0.11 min-1 for ..