Fig. 5. The enterins induce a hyperpolarization of the arterial muscle fibers. (A) Effect of ENpa on the membrane potential of the muscle fiber. ENpa was applied for 2 min at the concentrations indicated. (B) The concentration—response relationships of two enterins. Values are means ± S.E.M. (N=4-9) of the hyperpolarization plotted against the concentrations of enterins. The smooth lines are best-fits of the equation described in Materials and methods. r₁ and n were fixed to 0 and 1, respectively. r₂ and logx0 for each fitting were as follows, respectively: ENe, 13.2, -6.6; ENpa, 12.5, -7.0.