Mechanism of action of granulopoiesis inhibiting factor (chalone). I. Evidence for a receptor protein on bone marrow cells.

Rat bone marrow cells respond to granulopoiesis inhibiting factor by a reduced incorporation of tritiated thymidine. Cells treated with low concentrations of trypsin lose their ability to respond to the factor if protein synthesis is partially inhibited by low doses of cycloheximide. Responsiveness is retained if protein synthesis is permitted after enzyme treatment. The data suggest that a protein receptor on the external surface of the target cells is required for the action of granulopoiesis inhibiting factor on bone marrow cells.