Activation of Inward Rectifier K+ Channel 2.1 by PDGF‐BB in Rat Vascular Smooth Muscle Cells through Protein Kinase A

Figure 1. Effects of PDGF-BB on Kir2.x currents. (a) Original tracings illustrating currents determined in RASMCs. Membrane potential (Em) was held at -80 mV, and pulse potentials were applied from -150 mV to 0 mV. (b) Arithmetic mean ± SEM (n = 10) of current-voltage relationship curves. (c)Arithmetic mean ± SEM (n = 10) of the current amplitude at -150 mV of Kir2.x currents in Ba2+; CON. ∗P < 0.05 vs. Ba2+; PDGF-BB ∗∗P < 0.05 vs. CON; PDGF-BB+Ba2+. ∗∗∗P < 0.05 vs. PDGF-BB. (d) The “O” and “C” indicate the opened and closed states of Kir2.x currents, respectively. (e) Ba2+ attenuated and PDGF-BB increased the NPo of Kir2.x currents (at +70 mV) by 4.58 ± 0.33% and 78.82 ± 8.05% (∗∗P < 0.01 vs. CON, n = 5) compared to CON (43.29 ± 6.42%) (∗P < 0.01 vs. Ba2+, n = 5), and PDGF-BB+Ba2+ was 41.47 ± 6.13% (P < 0.01 vs. PDGF-BB, n = 5). (f) Time course of PDGF-BB action of Kir2.x currents. Averaged NPo plot (5 s bins) from five repeated perfusions of indicated compounds were normalized to control. CON means vascular smooth muscle cells without any drug intervention.

Figure 2. Effects of PDGF-BB on Kir2.1, Kir2.2, and Kir2.3 in transiently transfected HEK293 cells. (a–c) The transfections of the Kir2.1, Kir2.2, and Kir2.3 vector were verified by RT-PCR. (d–f) Arithmetic mean ± SEM (n = 10) of current-voltage relationship curves. (g) Arithmetic mean ± SEM (n = 10) of the current amplitude at -150 mV of Kir2.x currents in PDGF-BB; Kir2.1. ∗P < 0.05 vs. Kir2.2, Kir2.1; ∗∗P < 0.05 vs. Kir2.3. CON means vascular smooth muscle cells without any drug intervention.

Figure 3. Effects of PDGF-BBRα (-) and PDGF-BBRβ (-) on PDGF-BB-mediated activation of Kir2.1 currents. (a) Original tracings illustrating currents determined in RASMCs. Em was held at -80 mV, and pulse potentials were applied from -150 mV to 0 mV. (b) Arithmetic mean ± SEM (n = 10) of current-voltage relationship curves. (c) Arithmetic mean ± SEM (n = 10) of the current amplitude at -150 mV of Kir2.1 currents in PDGF-BB; PDGF-BBRα (-). P > 0.05 vs. PDGF-BB; PDGF-BBRβ (-). ∗P < 0.05 vs. PDGF-BB.

Figure 4. Effects of PKA and Akt on PDGF-BB-mediated activation of Kir2.1 currents. (a) Original tracings illustrating currents determined in RASMCs. Em was held at -80 mV, and pulse potentials were applied from -150 mV to 0 mV. (b) Arithmetic mean ± SEM (n = 10) of current-voltage relationship curves. (c) Arithmetic mean ± SEM (n = 10) of the current amplitude at -150 mV of Kir2.1 currents in PDGF-BB; PDGF-BB+Rp-8-CPT-cAMPs. Rp-8-CPT-cAMPs (10 μM). ∗P < 0.05 vs. PDGF-BB; PDGF-BB+GSK690693. GSK690693 (10 nM). P > 0.05 vs. PDGF-BB.

Figure 5. Effects of AC on PDGF-BB-mediated activation of Kir2.1 currents. (a) Original tracings illustrating currents determined in RASMCs. Em was held at -80 mV, and pulse potentials were applied from -150 mV to 0 mV. (b) Arithmetic mean ± SEM (n = 10) of current-voltage relationship curves. (c) Arithmetic mean ± SEM (n = 10) of the current amplitude at -150 mV of Kir2.1 currents in PDGF-BB; PDGF-BB+forskolin. Forskolin (10 μM). ∗P < 0.05 vs. PDGF-BB; PDGF-BB+SQ22536. SQ22536 (10 nM). ∗∗P < 0.05 vs. PDGF-BB. (d) The “O” and “C” indicate the opened and closed states of Kir2.1 currents, respectively. (e) The forskolin increased and SQ22536 decreased the NPo of Kir2.1 currents (at +70 mV) by 98.16 ± 8.61% (∗P < 0.05 vs. PDGF-BB, n = 5) and 8.73 ± 0.23% (∗∗P < 0.01 vs. PDGF-BB, n = 5) compared to PDGF-BB alone (70.23 ± 7.35%). (f) Time course of PDGF-BB action of Kir2.1 currents. Averaged NPo plot (5 s bins) from five repeated perfusions of indicated compounds was normalized to control.