Ventura C, Ferroni C, Flamigni F, Stefanelli C, Capogrossi M C
Institute of Biochemistry A. Bonsignore, University of Sassari, Italy.
Am J Physiol. 1994 Aug;267(2 Pt 2):H587-92. doi: 10.1152/ajpheart.1994.267.2.H587.
In electrically stimulated myocytes loaded with the fluorescent Ca2+ indicator indo 1-acetoxymethyl ester, spermine induced a dose-dependent (100-500 microM) negative inotropic effect, which was associated with a decrease in the magnitude of the cytosolic Ca2+ concentration ([Ca2+]i) transient but not with changes in myofilament responsiveness to Ca2+. Spermidine induced a less pronounced negative inotropic effect, whereas putrescine did not modify myocyte contraction. In the unstimulated state, spermine did not alter resting [Ca2+]i. Superfusion of the cardiac myocytes with 10 mM alpha-difluoromethylornithine, an inhibitor of polyamine synthesis, did not modify cellular responses to isoproterenol (10(-9)-10(-7) M). beta-Adrenergic stimulation did not affect either ornithine decarboxylase activity or intracellular polyamine levels within a 10-s to 15-min period of treatment. In summary, only exogenously administered polyamines were able to influence myocyte contractility. Their negative inotropic effect resulted from changes in [Ca2+]i homeostasis and required cellular depolarization.
在加载了荧光钙指示剂indo 1-乙酰氧基甲酯的电刺激心肌细胞中，精胺诱导了剂量依赖性（100 - 500微摩尔）的负性肌力作用，这与胞质钙浓度（[Ca2+]i）瞬变幅度的降低有关，但与肌丝对钙的反应性变化无关。亚精胺诱导的负性肌力作用较弱，而腐胺不改变心肌细胞收缩。在未刺激状态下，精胺不改变静息[Ca2+]i。用10 mM α-二氟甲基鸟氨酸（一种多胺合成抑制剂）对心肌细胞进行灌流，不改变细胞对异丙肾上腺素（10(-9) - 10(-7) M）的反应。β-肾上腺素能刺激在10秒至15分钟的治疗期内既不影响鸟氨酸脱羧酶活性，也不影响细胞内多胺水平。总之，只有外源性给予的多胺能够影响心肌细胞收缩力。它们的负性肌力作用源于[Ca2+]i稳态的变化，且需要细胞去极化。
