首页> 外文期刊>The biochemical journal >Effects of vasopressin and La3+ on plasma-membrane Ca2+ inflow and Ca2+ disposition in isolated hepatocytes. Evidence that vasopressin inhibits Ca2+ disposition
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Effects of vasopressin and La3+ on plasma-membrane Ca2+ inflow and Ca2+ disposition in isolated hepatocytes. Evidence that vasopressin inhibits Ca2+ disposition

机译:加压素和La3 +对离体肝细胞浆膜Ca2 +流入和Ca2 +处置的影响。加压素抑制Ca2 +沉积的证据

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pVasopressin caused a 40% inhibition of 45Ca uptake after the addition of 0.1 mM-45Ca2+ to Ca2+-deprived hepatocytes. At 1.3 mM-45Ca2+, vasopressin and ionophore A23187 each caused a 10% inhibition of 45Ca2+ uptake, whereas La3+ increased the rate of 45Ca2+ uptake by Ca2+-deprived cells. Under steady-state conditions at 1.3 mM extracellular Ca2+ (Ca2+o), vasopressin and La3+ each increased the rate of 45Ca2+ exchange. The concentrations of vasopressin that gave half-maximal stimulation of 45Ca2+ exchange and glycogen phosphorylase activity were similar. At 0.1 mM-Ca2+o, La3+ increased, but vasopressin did not alter, the rate of 45Ca2+ exchange. The results of experiments performed with EGTA or A23187 or by subcellular fractionation indicate that the Ca2+ taken up by hepatocytes in the presence of La3+ is located within the cell. The addition of 1.3 mM-Ca2+o to Ca2+-deprived cells caused increases of approx. 50% in the concentration of free Ca2+ in the cytoplasm [(Ca2+]i) and in glycogen phosphorylase activity. Much larger increases in these parameters were observed in the presence of vasopressin or ionophore A23187. In contrast with vasopressin, La3+ did not cause a detectable increase in glycogen phosphorylase activity or in [Ca2+]i. It is concluded that an increase in plasma membrane Ca2+ inflow does not by itself increase [Ca2+]i, and hence that the ability of vasopressin to maintain increased [Ca2+]i over a period of time is dependent on inhibition of the intracellular removal of Ca2+./p
机译:在向缺乏Ca2 +的肝细胞中添加0.1 mM-45Ca2 +后,Vasopressin抑制了45Ca的吸收40%。在1.3 mM-45Ca2 +时,加压素和离子载体A23187各自引起45Ca2 +吸收的10%抑制,而La3 +增加了Ca2 +缺乏细胞对45Ca2 +吸收的速率。在1.3 mM的稳态条件下,细胞外Ca2 +(Ca2 + o),加压素和La3 +各自增加了45Ca2 +交换的速率。能最大程度地刺激45Ca2 +交换和糖原磷酸化酶活性的血管加压素浓度相似。在0.1 mM-Ca2 + o处,La3 +增加,但加压素并未改变,45Ca2 +交换的速率。用EGTA或A23187或通过亚细胞分离进行的实验结果表明,存在La3 +的情况下肝细胞吸收的Ca2 +位于细胞内。向缺少Ca2 +的细胞中添加1.3 mM-Ca2 + o导致大约增加。细胞质[(Ca2 +] i)中游离Ca2 +的浓度和糖原磷酸化酶活性的50%。在存在加压素或离子载体A23187的情况下,观察到这些参数的增加幅度更大。与加压素相反,La3 +并未引起糖原磷酸化酶活性或[Ca2 +] i的可检测的增加。结论是,质膜Ca2 +流入量的增加本身并不增加[Ca2 +] i,因此,加压素在一段时间内维持增加的[Ca2 +] i的能力取决于抑制细胞内对Ca2 +的去除。

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