Figure 2.

Under stationary conditions, the cell population tends to maintain a certain value of the mean receptor occupancy r, regardless of the mean r_max. Plotted are the nullclines for zero net cell production (R_p = 0, Eq. 6C; solid curves) and for zero net PDGF production (k_s − k_uu − k_vvr = 0; dot-dashed curves). Their intersection point (dotted lines) determines the steady state in the absence of spatial gradients. The black curves are for the base case, r_max = 1; other r_max values (gray curves) are 0.3 and 3. (A) plotted in (r,v) phase space. (B) plotted in (u,v) phase space.