by Yanping Liu, Ken Terata, Nancy J. Rusch, and David D. Gutterman High Glucose Impairs Voltage-Gated K+ Channel Current in Rat Small Coronary Arteries by Yanping Liu, Ken Terata, Nancy J. Rusch, and David D. Gutterman Circulation Research Volume 89(2):146-152 July 20, 2001 Copyright © American Heart Association, Inc. All rights reserved.

Figure 1. A, Ethidium bromide fluorescence of rat small CAs incubated for 10 minutes in HE immediately after dissection (control) or after 24 hours in NG, LG, or HG. All image gain settings were identical. Figure 1. A, Ethidium bromide fluorescence of rat small CAs incubated for 10 minutes in HE immediately after dissection (control) or after 24 hours in NG, LG, or HG. All image gain settings were identical. Relative fluorescence intensity (red) corresponds to the rate of O2·− formation in the vessel wall. Exposure to HG increased the production of O2·− within the vessel wall. Dotted lines demonstrate edge of vessel wall. B, Relative intensity ratio of arteries exposed to NG, LG, and HG normalized to that of control vessels. The fluorescence intensity is significantly increased only in HG arteries (*P<0.05 vs NG and LG). Yanping Liu et al. Circ Res. 2001;89:146-152 Copyright © American Heart Association, Inc. All rights reserved.

Figure 2. A, Sample images comparing fluorescence intensity in freshly isolated arteries (control) and in arteries treated with HG with or without SOD and CAT. Fluorescence is markedly increased in HG arteries compared with control vessels. Figure 2. A, Sample images comparing fluorescence intensity in freshly isolated arteries (control) and in arteries treated with HG with or without SOD and CAT. Fluorescence is markedly increased in HG arteries compared with control vessels. SOD+CAT abolished ethidium bromide fluorescence in HG. Dotted lines indicate edge of vessel wall. B, Summary of fluorescence intensity (normalized to control) in 6 arteries from each group. Fluorescence intensity was significantly reduced in HG arteries treated with SOD and CAT (*P<0.05 vs HG). Yanping Liu et al. Circ Res. 2001;89:146-152 Copyright © American Heart Association, Inc. All rights reserved.

Figure 3. A, Whole-cell K+ current (IK) in coronary VSMCs from arteries incubated with NG, LG, and HG. Currents were elicited by incremental 10-mV depolarizing steps from −60 to 60 mV. Figure 3. A, Whole-cell K+ current (IK) in coronary VSMCs from arteries incubated with NG, LG, and HG. Currents were elicited by incremental 10-mV depolarizing steps from −60 to 60 mV. Cell capacitance was similar between cells: NG was 10 pF; LG, 11 pF; and HG, 10 pF. Compared with outward currents in cells from arteries incubated in NG or LG, outward currents in cells from arteries exposed to HG were reduced. 4-AP (3 mmol/L) blocked a large component of the outward current in cells from NG and LG arteries but caused less inhibition in cells from HG arteries. B, Current-voltage relationships of IK densities in cells from arteries exposed to NG, LG, or HG. Density was significantly reduced in cells from HG arteries compared with cells from NG and LG arteries (*P<0.05 vs NG and LG). C, Current-voltage relationships showing the effect of 4-AP on macroscopic IK in NG, LG, and HG cells. VSMCs from arteries incubated with HG show less 4-AP–sensitive IK compared with cells from arteries exposed to NG and LG (*P<0.05 vs NG and LG). D, Comparison of voltage dependence of IK between cells from NG and HG arteries. Inset shows sample traces of tail currents recorded at −60 mV after a prepulse step to 60 mV to maximally activated IK. The plot of peak tail current amplitudes vs prepulse potentials indicates that tail currents were reduced in cells from HG arteries, whereas voltage dependence of IK was not altered. Yanping Liu et al. Circ Res. 2001;89:146-152 Copyright © American Heart Association, Inc. All rights reserved.

Figure 4. Effect of O2·− generated by XA and XO on IK Figure 4. Effect of O2·− generated by XA and XO on IK. A, IKs generated at a membrane potential of +60 mV when the cell was superfused with XA, XA+XO, or XA+XO+4-AP. Figure 4. Effect of O2·− generated by XA and XO on IK. A, IKs generated at a membrane potential of +60 mV when the cell was superfused with XA, XA+XO, or XA+XO+4-AP. Current traces were not leak-subtracted. B, Averaged IK density as a function of membrane potential. XA+XO reduced IK density with no further reduction in response to 4-AP (*P<0.05 vs XA). C, Voltage dependence of IK in response to O2·− generation. XA+XO decreased peak tail current amplitudes (*P<0.05 vs XA) but had no significant effect on voltage dependence. Respective V0.5 and k values given by the Boltzmann equation are as follows: XA, −10 mV and 17; XA+XO, −9 mV and 18. Voltage protocol was the same as in Figure 3D. Yanping Liu et al. Circ Res. 2001;89:146-152 Copyright © American Heart Association, Inc. All rights reserved.

Figure 5. Current-voltage relationships comparing IK densities of patch-clamped NG, LG, or HG cells in response to SOD (150 U/mL) and CAT (500 U/mL). Figure 5. Current-voltage relationships comparing IK densities of patch-clamped NG, LG, or HG cells in response to SOD (150 U/mL) and CAT (500 U/mL). A and B, SOD and CAT did not alter IK density in cells from arteries incubated in NG or LG. C, However, SOD and CAT partially restored IK in cells from arteries incubated in HG (*P<0.05 vs control). Insets show original currents recorded at 60 mV before and after cells were superfused with SOD and CAT. Current traces were not subtracted. Yanping Liu et al. Circ Res. 2001;89:146-152 Copyright © American Heart Association, Inc. All rights reserved.

Figure 6. A, Effect of 4-AP on the resting diameter of rat CAs incubated with NG, LG, and HG is shown (*P<0.05 vs NG and LG). Figure 6. A, Effect of 4-AP on the resting diameter of rat CAs incubated with NG, LG, and HG is shown (*P<0.05 vs NG and LG). Contractions induced by 4-AP were reduced in arteries exposed to HG compared with those exposed to NG or LG (n=7 each). B, Similar contractile responses to graded doses of KCl were observed in arteries incubated with either HG or NG (n=6, P=NS). C, Nifedipine induced similar dilator responses (percent maximal [Max.] dilation) in arteries incubated with NG and HG (n=6, P=NS). Yanping Liu et al. Circ Res. 2001;89:146-152 Copyright © American Heart Association, Inc. All rights reserved.

Figure 7. Diameter changes of small CAs in response to 4-AP before and after SOD and CAT. A and B, SOD and CAT did not affect the amplitude of 4-AP–induced contractions in vessels incubated in either NG or LG, respectively (n=7, P=NS each). Figure 7. Diameter changes of small CAs in response to 4-AP before and after SOD and CAT. A and B, SOD and CAT did not affect the amplitude of 4-AP–induced contractions in vessels incubated in either NG or LG, respectively (n=7, P=NS each). C, SOD and CAT improved the contractile response to 4-AP in arteries incubated with HG (n=7) (*P<0.05 vs control). Yanping Liu et al. Circ Res. 2001;89:146-152 Copyright © American Heart Association, Inc. All rights reserved.