血管钠肽抑制异丙肾上腺素增强的大鼠心肌细胞钙瞬变

Vasonatrin peptide attenuates the enhancement of electrically-induced intracellular calcium transient by isoproterenol in rat cardiac myocytes

采用光谱荧光法研究血管钠肽(vasonatrin peptide,VNP)对心肌细胞内钙瞬变的作用及其机制,观察钠尿肽鸟苷酸环化酶(guanylate cyclase,GC)受体的特异性阻断剂(HS-142-1)、8-溴-环磷酸鸟苷(8-Br-cGMP)和镁蓝(methylene blue,MB)对心肌细胞内钙瞬变的影响。结果显示,异丙肾上腺素(isoproterenol,Iso)(10^(-10)～10^(-6)mol/L)可剂量依赖性地引起心肌细胞内钙瞬变增强,相对于对照组分别增强(13±8)%(P>0.05)、(26±13)%(P<0.05)、(66±10)%(P<0.01)、(150±10)%(P<0.01)和(300±25)%(P<0.01)。此效应可被β肾上腺素受体阻断剂普萘洛尔(10^(-6)mol/L)所阻断。VNP(10^(-10)～10^(-6)mol/L)可剂量依赖性地抑制Iso(10^(-8)mol/L)引起的心肌细胞内钙瞬变幅值的升高,相对于Iso(10^(-8)mol/L)分别减弱(99±3)%(P>0.05)、(96±2)%(P<0.05)、(84±6)%(P<0.01)、(66±3)%(P<0.01)和(62±3)%(P<0.01)。8-Br-cGMP(10^(-7)～10^(-3)mol/L)也可剂量依赖性地抑制Iso(10^(-8)mol/L)引起心肌细胞内钙瞬变的增强。HS-142-1(2×10^(-5)mol/L)使VNP的作用几乎完全消失。MB是GC的抑制剂,10^(-5)mol/L MB不但使VNP的作用完全消失,而且增强Iso对心肌细胞内钙瞬变的效应。VNP和HS-142-1本身对心肌细胞内钙瞬变无显著影响。而MB使心?

The purpose of this study was to investigate the effects of vasonatrin peptide (VNP) on electrically-induced intracellular calcium ([Ca^(2+)]_i) transient and mechanism of the effects in the cardiac myocytes. The [Ca^(2+)]_i transient was measured with a fluoremetric method. The effects of HS-142-1, 8-Br-cGMP and methylene blue (MB) on [Ca^(2+)]_i, transient in cardiac myocytes were also determined. Isoproterenol (Iso) at 10^(-10)～10^(-6) mol/L augmented electrically-induced [Ca^(2+)]_i transient dose-dependently, which was (13±8)% (P>0. 05), (26±13)% (P<0.05), (66±10)% (P<0.01), (150±10)% (P<0.01) and (300±25)% (P<0.01), respectively. These effects were blocked by an β-adrenergic bloker propranolol (10^(-6) mol/L). The effect of Iso (10^(-8) mol/L) on [Ca^(2+)]_i, transient was attenuated in a dose-dependent manner by VNP at 10^(-10)～10^(-6) mol/L, which was (99±3)% (P>0.05), (96±2)% (P<0.05), (84±6)% (P<0.01), (66 ±3)% (P<0.01) and (62±3)% (P<0.01), respectively. 8-Br-cGMP (10^(-7)～10^(-3) mol/L) aslo attenuated 10^(-8) mol/L Iso-induced [Ca^(2+)]_i transient dose-dependent. The effect of VNP on [Ca^(2+)]_i, transient was almost abolished in the presence of HS-142-1(2×10^(-5) mol/L), an antagonist of the natriuretic peptide guanylate cyclase (GC) receptors. MB (10^(-5) mol/L), an inhibitor of GC, not only blocked the effect of VNP in myocytes, but also augmented electrically-induced [Ca^(2+)]_i transient. VNP and HS-142-1 themselves didn't change the [Ca^(2+)]_i transient in the cardiac myocytes significantly. But MB augmented the [Ca^(2+)]_i, transient in the cardiac myocytes significantly. These results suggest that VNP attenuates [Ca^(2+)]_i, transient induced by Iso. This effect is possibly achieved by binding VNP with the natriuretic peptide GC receptors in the myocytes, leading to an increase in intracellular cGMP.