Study of an inhibiting factor of epidermal proliferation in plucked skin and various tumours of mice.

The aim of our research was to investigate, by autoradiographic methods, the presence of an inhibitory factor (IF) in normal skin, in plucked skin and in five experimental skin tumors of the mouse, capable of inhibiting epidermal proliferation. The experimental model used was that of Bullough & Laurence (1960), i.e. a wound in the ear of a mouse. After tritiated thymidine administration the measurement of the labelling index confirmed the existence of an inhibitory substance in normal skin. The plucked skin had no inhibitory effect when it was taken 24 h after plucking, but after 4 days its effect had returned to normal. The skin tumours, whether epithelial or mesenchymal, showed the same inhibitory effect as normal skin whereas a non-cutaneous tumour tested had no inhibitory effect.