Dual role of calcium-activated potassium channels of high conductance: facilitator or limiter of NO-induced arterial relaxation?

Figures

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  FIGURE 1. Schematic representation of the experimental protocol used in this study, see text for details. CRR–concentration response relationship, W–washout, IBTX–iberiotoxin, SNP–sodium nitroprusside.

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  FIGURE 2. Anticontractile effect of SNP in the absence and presence of BKCa channel blockade at different levels of contractility in rat tail arteries. (A, C, E) Concentration–response relationships for methoxamine in the absence of any additional substances (control), in the presence of iberiotoxin (0.1 µM, IBTX), sodium nitroprusside (0.1 µM, SNP) or iberiotoxin together with sodium nitroprusside (IBTX + SNP). Data analysis was limited to the respective highlighted areas corresponding to low (A), middle (C) and high (E) levels of contractility. n = 10; * - p < 0.05 (repeated measures ANOVA with two-stage linear step-up procedure of Benjamini, Krieger and Yekutieli). (B, D, F) Anticontractile effect of SNP in the absence (circles, Control) and in the presence of IBTX (squares, IBTX), presented as the difference between the area under the concentration-response relationships in the control and the SNP groups as well as in the IBTX and the IBTX + SNP groups. n = 10; # - p < 0.05 (Mann-Whitney test), $ - p < 0.05 (Welch’s t-test), n.s. – non-significant.

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  FIGURE 3. Anticontractile effect of SNP in the absence and presence of BKCa channel blockade at different levels of contractility in rat saphenous arteries. (A, C) Concentration–response relationships for methoxamine in the absence of any additional substances (control), in the presence of iberiotoxin (0.1 µM, IBTX), sodium nitroprusside (0.1 µM, SNP) or iberiotoxin together with sodium nitroprusside (IBTX + SNP). Data analysis was limited to the respective highlighted areas corresponding to low (A) and high (C) levels of contractility. n = 8; * - p < 0.05 (repeated measures ANOVA with two-stage linear step-up procedure of Benjamini, Krieger and Yekutieli). (B, D) Anticontractile effect of SNP in the absence (circles, Control) and in the presence of IBTX (squares, IBTX), presented as the difference between the area under the concentration-response relationships in the control and the SNP groups as well as in the IBTX and the IBTX + SNP groups. n = 8; $ - p < 0.05 (Welch’s t-test).

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  FIGURE 4. Anticontractile effect of SNP in the absence and presence of BKCa channel blockade at different levels of contractility in rat left coronary arteries. (A, C) Concentration–response relationships for serotonin in the absence of any additional substances (control), in the presence of iberiotoxin (0.1 µM, IBTX), sodium nitroprusside (0.1 µM, SNP) or iberiotoxin together with sodium nitroprusside (IBTX + SNP). Data analysis was limited to the respective highlighted areas corresponding to low (A) and high (C) levels of contractility. n = 10; * - p < 0.05 (repeated measures ANOVA with two-stage linear step-up procedure of Benjamini, Krieger and Yekutieli). (B, D) Anticontractile effect of SNP in the absence (circles, Control) and in the presence of IBTX (squares, IBTX), presented as the difference between the area under the concentration-response relationships curves in the control and the SNP groups as well as in the IBTX and the IBTX + SNP groups. n = 10; $ - p < 0.05 (Welch’s t-test), # - p < 0.05 (Mann-Whitney test).

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  FIGURE 5. Anticontractile effect of SNP in the absence and presence of BKCa channel blockade at different levels of contractility in rat right coronary arteries. (A, C) Concentration–response relationships for serotonin in the absence of any additional substances (control), in the presence of iberiotoxin (0.1 µM, IBTX), sodium nitroprusside (0.1 µM, SNP) or iberiotoxin together with sodium nitroprusside (IBTX + SNP). Data analysis was limited to the respective highlighted areas corresponding to low (A) and high (C) levels of contractility. n = 9; *- p < 0.05 (repeated measures ANOVA with two-stage linear step-up procedure of Benjamini, Krieger and Yekutieli). (B, D) Anticontractile effect of SNP in the absence (circles, Control) and in the presence of IBTX (squares, IBTX), presented as the difference between the area under the concentration-response relationships in the control and the SNP groups as well as in the IBTX and the IBTX + SNP groups. n = 9; # - p < 0.05 (Mann-Whitney test).