Binet A, Berthon B, Claret M
Biochem J. 1985 Jun 15;228(3):565-74. doi: 10.1042/bj2280565.
The action of alpha 1-adrenergic agonists (noradrenaline in the presence of propranolol), vasopressin and angiotensin on the intracellular free Ca2+ concentration, [Ca2+]i, was determined by using the fluorescent dye quin2 in isolated rat liver cells. In the presence of external Ca2+ (1.8 mM), 1 microM-noradrenaline induced an increase in [Ca2+]i up to about 800 nM without apparent delay, whereas 10 nM-vasopressin and 1 nM-angiotensin increased [Ca2+]i to values higher than 1500 nM with a lag period of about 6s. The successive addition of the hormones and of their specific antagonists indicated that the actions of the three Ca2+-mobilizing hormones occurred without apparent desensitization (over 6 min) and via independent receptors. The relative contributions of internal and external Ca2+ pools to the cell response were determined by studying the hormone-mediated [Ca2+]i increase and glycogen phosphorylase activation in low-Ca2+ media (22 microM). In this medium: (1) [Ca2+]i was lowered and the hormones initiated a transient instead of a sustained increase in [Ca2+]i; subsequent addition (2 min) of a second hormone promoted a lesser increase in [Ca2+]i; in contrast, the subsequent addition (2 min) of Ca2+ (1.8 mM) caused [Ca2+]i to increase to a value close to that initiated by the hormone in control conditions, the amplitude of the latter response being dependent on the concentration of Ca2+ added to the medium; (2) returning to normal Ca2+ (1.8 mM) restored the resting [Ca2+]i and allowed the hormone added 2 min later to promote a large increase in [Ca2+]i whose final amplitude was also dependent on the concentration of Ca2+ added beforehand. Similar results were found when the same protocol was applied to the glycogen phosphorylase activation. It is concluded that Ca2+ influx is required for a maximal and sustained response and to reload the hormone-sensitive stores.
使用荧光染料喹啉-2，在分离的大鼠肝细胞中测定了α1 -肾上腺素能激动剂（在普萘洛尔存在下的去甲肾上腺素）、血管加压素和血管紧张素对细胞内游离钙离子浓度（[Ca2+]i）的作用。在存在细胞外钙离子（1.8 mM）的情况下，1 μM去甲肾上腺素可使[Ca2+]i迅速升高至约800 nM，无明显延迟，而10 nM血管加压素和1 nM血管紧张素则使[Ca2+]i升高至高于1500 nM的值，有大约6秒的延迟期。依次添加激素及其特异性拮抗剂表明，这三种钙离子动员激素的作用在无明显脱敏（超过6分钟）的情况下通过独立受体发生。通过研究在低钙离子培养基（22 μM）中激素介导的[Ca2+]i升高和糖原磷酸化酶激活，确定了细胞内和细胞外钙离子库对细胞反应的相对贡献。在这种培养基中：（1）[Ca2+]i降低，激素引发[Ca2+]i的短暂而非持续升高；随后添加（2分钟）第二种激素促进[Ca2+]i的升高较小；相反，随后添加（2分钟）钙离子（1.8 mM）使[Ca2+]i升高至接近对照条件下激素引发的值，后者反应的幅度取决于添加到培养基中的钙离子浓度；（2）恢复到正常钙离子浓度（
