Objective: To study the effect of KATP channel opener and its possible mechanism on the sinoatrial node cells of neonatal rats which were cultured under simulated ischemia-reperfusion. Methods: Freshly isolated sinoatrial node (SAN) cells of neonatal rats were purified and cultured for 2 d, and then they were randomly divided into the control, simulated ischemia-reperfusion group (I/R group), group intervened with KATP channel opener pinacidil (P+I/R group), KATP Channel blocking agent 5-HD (5-HD+I/R group), and group with the 2 agents at same time (5-HD+P+I/R group). The survival rate of cells was measured by flow cytometry and the content of intracellular calcium in the cells of each group was detected with laser confocal microscopy. Results: ① The survival rate of SAN cells in I/R group [(51.79±6.28)%] was remarkably significantly lower than in control [(95.08±10.48)%] (P<0.001), and very significantly lower than in P+I/R group [(63.77±5.35)%] (P<0.01), however, those of 5-HD+P+I/R group [(52.88±6.25)%] and 5-HD+I/R group [(53.16±5.35)%] was significantly lower compared with that in P+I/R group (P<0.01); ② When the average fluorescence intensity of sinoatrial node cells in the control was regarded as 100%, the relative fluorescence intensities of each group were: (374±52)% in I/R group, significantly higher than that of control (P<0.01); (162±20)% in P+I/R group, declining significantly than that of I/R group (P<0.01); (385±56)% in 5-HD+P+I/R group and (379±44)% in 5-HD+I/R group, increasing significantly than that of I/R group (P<0.01). Conclusion: ① Simulated ischemia-reperfusion can significantly reduce the survival rate of SAN cells, and can also lead to the overload of intracellular calcium in them. ② KATP channel opener, pinacidil, exerts protective effect on the cells under simulated ischemia-reperfusion, which may be associated with the decrease of intracellular calcium loading in them.
To study the effect of simulated ischemia-reperfusion (I/R) on If of sinoatrial node (SAN) cellsand the ntervention of KATP channel opener Pinacidil. Methods: The SAN cells of the neonatal rats were detached and pu-rified 2 d efore the experiment. The experimental animals were randomly divided into the control group, group of simulatedI/R, group intervened with KATP channel opener Pinacidil (P + I/R) and group intervened with KATP channel blockingagent 5-HD (5-HD + P + I/R & 5-HD + I/R). The If density of each group was measured by technique of routine whole elldifferent directive potentials, the If density of the SAN cells in I/R group increased significantly, compared with that in thecontrol group ( P ＜ 0.01 ); that in P + I/R group decreased significantly, compared with that in I/R group ( P ＜ 0.01 ); theIf density values in 5-HD + P + I/R group and 5-HD + I/R group increased significantly, compared with that in P + I/Red curve of the SAN cells moved rightwards under ultimate activating potential, half of which was from - 108.0 ± 12.4 to- 89.5 ± 7.2 mV ( P ＜ 0.01 ); compared with that in I/R group, If activated curve of the SAN cells moved leftwards underultimate activating potential, half of which was the range from - 99.5 ± 10.8 mV ( P ＜ 0.05 ); KATP channel blockingagent 5-HD could block the effect of Pinacdil on If activated curve. Conclusion: KATP channel opener Pinacidil can antago-nize the effect of simulated I/R on the If of SAN cells, which may be beneficial to the maintenance of the relative stability ofion steady state and electrophysiological activities under condition of simulated I/R.
