Fan C C, Koenig H
Neurology Service, VA Lakeside Medical Center, Chicago, IL 60611.
J Mol Cell Cardiol. 1988 Sep;20(9):789-99. doi: 10.1016/s0022-2828(88)80004-x.
The beta-adrenergic agonist 1-isoproterenol induced an early (less than 1 min) stimulation of endocytosis, amino acid transport and hexose transport, monitored by the temperature-sensitive uptake of horseradish peroxidase, alpha-aminoisobutyrate and 2-deoxyglucose, respectively, in rat ventricle cubes. This stimulation was time- and concentration-dependent and was maximum at 10(-8) M isoproterenol. The beta-adrenergic antagonist propranolol blocked isoproterenol stimulation of membrane transport, thereby confirming beta-adrenoceptor mediation; 2.5 mM EGTA, 1 mM LaCl2 and 100 microM verapamil blocked the hormonal response without affecting basal transport. The calcium ionophore A23187 caused an acute stimulation of endocytosis, hexose and amino acid transport. Isoproterenol rapidly (less than 30 s) stimulated 45Ca2+ influx. These data suggest that stimulus-response (stimulus-"transport") coupling is mediated by a rise in cytosolic Ca2+ concentration. A rapid (less than 30 to 60 s) increase in ornithine decarboxylase (ODC) activity, followed by an early (less than 1 to 2 min), sustained increase in putrescine, spermidine and spermine concentrations was evoked by 10(-7) M isoproterenol. The ODC inhibitor alpha-difluoromethylornithine (DFMO, 5 mM) suppressed the isoproterenol-induced increase in ODC and polyamine levels and the stimulation of 45Ca influx, endocytosis, hexose transport, and amino acid transport. Putrescine (0.5 mM) negated DFMO inhibition and restored the increase in polyamines, 45Ca influx, endocytosis, and transport of hexose and amino acid. These data suggest that polyamine synthesis is involved in isoproterenol stimulation of Ca2+ influx and membrane transport functions in ventricular myocardium. These findings are consistent with a model for signal transduction and stimulus-response coupling in which polyamines function as intracellular messengers to generate cytosolic Ca2+ signals by stimulating Ca2+ influx.
β-肾上腺素能激动剂1-异丙肾上腺素可诱导大鼠心室肌小块早期（不到1分钟）内吞作用、氨基酸转运和己糖转运的刺激，分别通过辣根过氧化物酶、α-氨基异丁酸和2-脱氧葡萄糖的温度敏感摄取进行监测。这种刺激具有时间和浓度依赖性，在10^(-8) M异丙肾上腺素时达到最大值。β-肾上腺素能拮抗剂普萘洛尔可阻断异丙肾上腺素对膜转运的刺激，从而证实β-肾上腺素能受体介导作用；2.5 mM乙二醇双（2-氨基乙基醚）四乙酸（EGTA）、1 mM氯化镧和100 μM维拉帕米可阻断激素反应，而不影响基础转运。钙离子载体A23187可引起内吞作用、己糖和氨基酸转运的急性刺激。异丙肾上腺素可迅速（不到30秒）刺激45Ca2+内流。这些数据表明，刺激-反应（刺激-“转运”）偶联是由细胞质Ca2+浓度升高介导的。10^(-7) M异丙肾上腺素可引起鸟氨酸脱羧酶（ODC）活性迅速（不到30至60秒）增加，随后腐胺、亚精胺和精胺浓度早期（不到1至2分钟）持续增加。ODC抑制剂α-二氟甲基鸟氨酸（DFMO，5 mM）可抑制异丙肾上腺素诱导的ODC和多胺水平升高以及45Ca内流、内吞作用、己糖转运和氨基酸转运的刺激。腐胺（0.5 mM）可消除DFMO的抑制作用，并恢复多胺、45Ca内流、内吞作用以及己糖和氨基酸转运的增加。这些数据表明，多胺合成参与了异丙肾上腺素对心室心肌Ca2+内流和膜转运功能的刺激。这些发现与信号转导和刺激-反应偶联模型一致，在该模型中，多胺作为细胞内信使，通过刺激Ca2+内流产生细胞质Ca2+信号。
