TROPHIC ACTIONS OF CILIARY NEUROTROPHIC FACTOR ON MURINE EMBRYONIC CARCINOMA-CELLS

Recombinant rat CNTF (ciliary neurotrophic factor) at picomolar concen tration prevents the death of P19 murine embryonic carcinoma cells tha t usually follows upon withdrawal of serum from the culture medium. Fo r prolonged survival of P19 cells in serum-free medium, insulin must a lso be present. In the presence or absence of serum, CNTF stimulates t he differentiation of P19 cells, inducing the formation of neurites an d synthesis of neurofilament. The results of radioautographic studies with radioiodinated CNTF indicate the presence of high-affinity bindin g sites on P19 cells. Equilibration of P19 cells with [I-125]CNTF foll owed by incubation with cross-linking reagents reveals evidence for at least two putative receptors of approximately 78 and approximately 16 7 kDa.