Endothelin and increased contractility in adult rat ventricular myocytes. Role of intracellular alkalosis induced by activation of the protein kinase C-dependent Na(+)-H+ exchanger.
Endothelin and increased contractility in adult rat ventricular myocytes. Role of intracellular alkalosis induced by activation of the protein kinase C-dependent Na(+)-H+ exchanger.
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内皮素和成年大鼠心室肌细胞收缩力的增加。
DOI：
10.1161/01.res.68.1.269
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发表时间：
1991
影响因子：
20.1
通讯作者：
Kelly,RA
中科院分区：
文献类型：
--
作者：
Krämer,BK;Smith,TW;Kelly,RA
内皮素是一种由21个氨基酸组成的血管活性肽，是哺乳动物心脏中最有效的正性肌力药物之一。已经证明内皮素的变力作用部分是由于心肌肌丝对细胞内钙的明显敏感性，我们确定这是否可能是由于细胞内pH值（pHi）升高。在负载H（+）-选择性荧光探针BCECF的分离的成年大鼠心室细胞中，100 pM内皮素使收缩幅度增加至基线的190 +/- 26%，pHi增加0.08 +/- 0.02（n = 8），而1 nM内皮素使pHi增加0.13 +/- 0.03，收缩力几乎没有进一步增加。阿米洛利（10（-4）M）阻止了内皮素引起的pHi升高，并使变力性反应降低了45%，尽管随后的氯化铵诱导的碱化可以很容易地恢复变力性作用。同样，蛋白激酶C抑制剂（H-7和鞘氨醇）减少或消除了内皮素灌注后pHi的上升，同时导致其变力作用下降，与阿米洛利观察到的。百日咳毒素预处理，我们已经证明结果在完整的ADP-核糖基化的α-亚基的Go和Gi GTP结合蛋白和废除内皮素的正性肌力作用，只有部分减少了细胞内碱化诱导的肽，这表明一个复杂的信号转导机制。因此，内皮素的正性肌力作用部分是由于通过蛋白激酶C介导的途径刺激肌膜Na（+）-H+交换，导致pHi升高和心肌肌丝对细胞内Ca 2+的敏感性。
Endothelin, a 21-amino acid vasoactive peptide, is among the most potent positively inotropic agents yet described in mammalian heart. Having demonstrated that endothelin's inotropic effect is due, in part, to an apparent sensitization of cardiac myofilaments to intracellular calcium, we determined whether this could be due to a rise in intracellular pH (pHi). In isolated adult rat ventricular cells loaded with the H(+)-selective fluorescent probe BCECF, 100 pM endothelin increased contractile amplitude to 190 +/- 26% of baseline and pHi by 0.08 +/- 0.02 (n = 8), whereas 1 nM endothelin increased pHi by 0.13 +/- 0.03 with little further increase in contractility. Amiloride (10(-4)M) prevented the increase in pHi in response to endothelin and reduced the inotropic response by 45%, although the inotropic effect could be readily restored by subsequent NH4Cl-induced alkalinization. Similarly, inhibitors of protein kinase C (H-7 and sphingosine) diminished or abolished the rise in pHi after endothelin superfusion while causing a decline in its inotropic effect comparable with that observed with amiloride. Pretreatment with pertussis toxin, which we have demonstrated results in complete ADP-ribosylation of the alpha-subunits of Go and Gi GTP-binding proteins and abolition of endothelin's positive inotropic effect, only partially reduced the intracellular alkalinization induced by the peptide, suggesting a complex signal transduction mechanism. Thus, the positive inotropic action of endothelin is due in part to stimulation of the sarcolemmal Na(+)-H+ exchanger by a protein kinase C-mediated pathway, resulting in a rise in pHi and sensitization of cardiac myofilaments to intracellular Ca2+.