Heterologous regulation of EGF receptor function in cultured aortic smooth muscle cells

A10 cultured smooth muscle cells from rat embryonic thoracic aorta bound ¹²⁵I-labelled epidermal growth factor (¹²⁵I-EGF), and responded to EGF by an increase in DNA synthesis. Scatchard analysis of binding data obtained at 4° C showed curvilinearity consistent with there being two affinity classes of binding site. The amount of ¹²⁵I-EGF that bound was decreased by treatment of the A10 cells at 37° C with [Arg⁸]vasopressin or with 5-hydroxytryptamine (5-HT). Scatchard analysis of binding (at 4° C after pretreatment at 37° C) revealed this effect to be due to a loss of the high-affinity component of ¹²⁵I-EGF binding, with no change in total receptor number. The presence of vasopressin or 5-HT raised the concentration of EGF required for the stimulation of DNA synthesis. Cultured A10 aortic smooth muscle cells therefore have receptors for EGF that mediate an increase in cell proliferation. EGF receptor function is modified by vasopressin and 5-HT, probably as a consequence of their effects on EGF receptor affinity.