Kidney epithelial cells release growth factors in response to extracellular signals.

The growth of nontransformed monkey kidney epithelial cells in culture appears to be regulated by the interplay of positive and negative autocrine growth factors. Reduction of the potassium or sodium concentration of the medium induces rapid release of novel growth-promoting activities, whereas addition of the mitogen adenosine diphosphate stimulates the appearance of a platelet-derived growth factor-like protein which could function in a paracrine manner. These observations suggest that autocrine and paracrine growth factors could play an important role in physiological and pathological states in the kidney.