Figure 7.

I–V relationships for the insulin-sensitive K permeability in the basolateral membrane. Insulin-activated currents were obtained from amphotericin B–permeabilized monolayers in response to a voltage step protocol from −90 to +90 mV in 15-mV increments at a holding potential of 0 mV. The apical surface of the epithelium was bathed in KMeSO₄ Ringer solution without NaCl and permeabilized with amphotericin B. Standard (SR) or KCl Ringer solution was used to bathe the basolateral surface of the epithelium. Insulin (850 nM) was added to the basolateral solution of the cell monolayers maintained in serum-free media for 2 d. Mean reversal potentials for the insulin-sensitive currents were −53 ± 3 mV in standard (○, n = 9, N = 4) and 3 ± 2 mV in KCl (•, n = 6, N = 4) Ringer solution.