Figure 7: pH dependence of effects of guanylin peptides on membrane voltages ( ) of human proximal tubule cells. Guanylin (GN) depolarized cells at pH 5.5 as well as pH 8.0. Uroguanylin (UGN) at pH 5.5, activated GC-C and depolarized cells while at pH 8.0 decreased affinity of GC-C for UGN and GC-C independent, G-protein-coupled receptor is activated which leads to hyperpolarization of the cells. Mean values: SEM. Modified from Sindiće et al. [21].