Figure 8.

I–V relationships for the benzamil-sensitive permeability in the apical membrane. Benzamil-sensitive current obtained from amphotericin B–permeabilized monolayers in response to a voltage step protocol from −90 to +165 mV in 15-mV increments from a holding potential of 0 mV. Experiments were performed under conditions where the basolateral surface was bathed in KMeSO₄ Ringer solution with 5 mM NaCl and permeabilized with amphotericin B. NaMeSO₄ Ringer solution with 5 mM KCl was used to bathe the apical surface of the epithelium. Benzamil (5 μM) was added to the apical solution of the cell monolayers grown in serum-free media (control) or serum-free media pretreated with 850 nM insulin for 30 min (short term) or serum-free media supplemented with 850 nM insulin for 4 d (long term). Mean reversal potentials for benzamil-sensitive currents were 72 ± 4 mV for control (○, n = 5, N = 3), 69 ± 8 mV for short-term (•, n = 6, N = 3), and 65 ± 4 mV for long-term (▵, n = 7, N = 4) insulin treatment.