Villalba M, Zabala M T, Martinez-Serrano A, de la Colina R, Satrústegui J, Garcia-Ruiz J P
Departamento de Biología Molecular, Universidad Autónoma de Madrid, Spain.
Endocrinology. 1991 Dec;129(6):2857-61. doi: 10.1210/endo-129-6-2857.
PRL at a physiological concentration (10(-8) M) produced a very rapid and transient increase in 45Ca efflux in freshly isolated hepatocytes, which reached the highest value within 5 min and returned to baseline level after 20 min. PRL-induced 45Ca2+ efflux resulted in a loss of 15% of total cell calcium, which was similar to that found in vasopressin-treated cells. However, in contrast with the PRL effect, 45Ca2+ efflux induced by vasopressin was sustained. We demonstrate by using two different approaches, glycogen phosphorylase-a activation and direct cytosolic calcium concentration [( Ca2+]i) measurements, that PRL elicits a [Ca2+]i increase. The treatment of hepatic cells with PRL caused a 4-fold stimulation in glycogen phosphorylase-alpha activity after 2 min of PRL addition. Direct [Ca2+]i determination in fluo-3-loaded hepatocytes showed a 11% increase after 5 min of PRL addition. Similar data were observed in hepatocytes stimulated either with vasopressin (10(-7) M) or calcium ionophore A23187 (200 nM). The increase in [Ca2+]i promoted by PRL was independent of extracellular calcium or voltage-operated calcium channels. The data demonstrate that calcium is involved in the intracellular signaling of PRL in liver cells and that PRL initiates its action by a Ca2+ mobilization from the intracellular stores.
生理浓度（10⁻⁸ M）的催乳素（PRL）可使新鲜分离的肝细胞中⁴⁵Ca外流迅速且短暂增加，在5分钟内达到最高值，并在20分钟后恢复到基线水平。PRL诱导的⁴⁵Ca²⁺外流导致细胞总钙含量损失15%，这与在血管加压素处理的细胞中发现的情况相似。然而，与PRL的作用相反，血管加压素诱导的⁴⁵Ca²⁺外流是持续的。我们通过使用两种不同的方法，即糖原磷酸化酶-a激活和直接测量胞质钙浓度[Ca²⁺]i，证明PRL会引起[Ca²⁺]i增加。用PRL处理肝细胞2分钟后，糖原磷酸化酶-α活性增加了4倍。在添加PRL 5分钟后，对负载氟-3的肝细胞进行直接[Ca²⁺]i测定显示增加了11%。在用血管加压素（10⁻⁷ M）或钙离子载体A23187（200 nM）刺激的肝细胞中也观察到了类似的数据。PRL促进的[Ca²⁺]i增加与细胞外钙或电压门控钙通道无关。这些数据表明钙参与了肝细胞中PRL的细胞内信号传导，并且PRL通过从细胞内储存库中动员Ca²⁺来启动其作用。
