Multiple responses of connective tissue cells to mitogenic stimulation with platelet-derived growth factor

A number of important properties are held by mitogenic substances such as platelet derived growth factor for cells that can respond to such a mitogen. These include responses that occur early after exposure of the cells to the mitogens. Such responses include increases in endocytosis, binding of low density lipoprotein to high affinity cell surface receptors and increased uptake and degradation of LDL, increases in phospholipid metabolism, sodium and potassium ion flux, increases in protein and RNA synthesis, and chemotaxis. It is not yet clear whether some of these properties can be separated from the stimulus to enter DNA synthesis and mitosis, or whether they are tightly coupled to the latter. Nevertheless, they all precede DNA synthesis by many hours before the cells enter into S and go on to divide. It is highly probable that a number of other biological events will be found to be stimulated by exposing cells to mitogens, such as the platelet derived growth factor. Elucidation of these events and determination of the interrelation of each of these biological responses to the subsequent multiplication of the cells in a given set of circumstances will help to provide a basis for understanding how these mitogens work, and potentially how it may be possible to prevent some of the proliferative responses that represent such an inherent part of many disease processes.