Fig. 3

Activation of whole cell currents by hypotonic solutions in ventricular myocyte from normal and STZ-diabetic mice. a, b Time course of activation of VRAC currents at +60 mV (filled circle) and −60 mV (circle) observed in the myocytes of normal (a) and STZ-diabetic (b) mice exposed to hypotonic (HYPO) solutions. [Cl⁻]_o/[Cl⁻]_i ratio was constantly 105 mM/45 mM with which the predicted equilibrium potential (E _Cl) was −21 mV. The cells were initially bathed in isotonic solution (ISO), and then hypotonic (HYPO) solution was applied during the period indicated by bar. The pulse protocol is shown in the upper part of b. c and d Recordings of membrane currents in myocytes from normal (c) and STZ-diabetic mice (d) in isotonic and hypotonic solutions, respectively. Currents were recorded by applying 400 ms voltage-clamp steps to membrane potentials between −100 and +100 mV in +20 mV steps from a holding potential of −40 mV every 6 s, at the time points (a and b) indicated in a and b. e The mean I–V relationships of the difference current between the current in HYPO and that in ISO (a, b in c and d), obtained in myocyte from normal (filled circle) and STZ-diabetic (filled square) mice. Arrow indicates the predicted Cl⁻ equilibrium potential. f Mean time course of activation of VRAC current at +60 mV after hypotonic solutions, in myocytes from normal (filled circle) and STZ-diabetic mice (filled square). In this plot, the current level at the beginning of hypotonic perfusion (0 min) was set to be 0. Abscissa, time after exposure to hypotonic solution. *Significantly smaller than the control value at matched time point with P < 0.05 according to an unpaired t-test. A comparison of curves with repeated measures ANOVA yielded P < 0.01 (¶¶)