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. .