The effect of the plant hormone indole-3-acetic acid and chemically related compounds on the growth of mouse fibroblast 3T3 cells.

1. The effect of the plant hormone indole-3-acetic acid (IAA) and the chemically related compounds: serotonin, tryptophan, I. pyruvic, I. butyric, I. propionic and tryptamine on the growth of 3T3 cells has been studied. 2. Each of these compounds increases the cell number in a variable degree. The increase is related to the presence of the serum in the medium. 3. The kinetic relation between IAA, foetal calf serum and cell growth was studied. 4. It may be that IAA and related compounds affect the cell growth through adenylate cyclase and cAMP-cGMP systems.