Fig. 6

Effects of PIP3 loading on VRAC currents in ventricular myocytes from STZ-diabetic mice. a and b, Recordings of membrane currents in myocytes from STZ-diabetic mice in isotonic (ISO) and hypotonic (HYPO) solutions. The cells were loaded with PIP2 (a) or PIP3 (b). Voltage pulses were applied as in Fig. 3c and d. c Mean I–V relationships of VRAC current in ventricular myocyte from STZ-diabetic mice dialyzed with PIP2 (circle, n = 5) or PIP3 (filled circle, n = 5). In this series of experiments, pipette solution contained 10 μM of PIP2 or PIP3, and the current recordings were begun ~ 30 min after the membrane rupture, for more complete cell dialysis. d Mean time course of activation of VRAC current at +60 mV after hypotonic solutions, in STZ-diabetic myocyte dialyzed with PIP2 (circle) and PIP3 (filled circle). 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 (¶¶). e Mean density of VRAC current at +100 mV obtained under different conditions. Currents were measured in cells from normal and STZ-diabetic mice, with intracellular PIP2 or PIP3, respectively. f Mean density of VRAC current at +100 mV in normal (Normal) and STZ-diabetic (STZ) myocytes incubated with wortmannin (100 nM) for 5–8 h. In e and f, dashed line indicates the control level derived from the data in Fig. 3e (filled circle). * and **Significantly smaller than control with P < 0.05 and 0.01, respectively, according to one-way ANOVA with post-hoc test. Number in parentheses indicates number of cells examined