Sodium fluxes in human fibroblasts: Kinetics of serum‐dependent and serum‐independent pathways
Sodium fluxes in human fibroblasts: Kinetics of serum‐dependent and serum‐independent pathways
复制标题
人成纤维细胞中的钠通量：血清依赖性和血清非依赖性途径的动力学
DOI：
--
复制
发表时间：
1981
影响因子：
5.6
通讯作者：
M. Villereal
中科院分区：
文献类型：
--
作者：
M. Villereal
血清剥夺的人成纤维细胞中的钠流入是通过显示饱和动力学的途径进行的。初始 Na 流入量与 [Na]o ([Na]i = 10 mM) 的关系图给出了一条简单的米氏曲线，其中 K1/2 = 70.0 ± 8.1 mM 和 Vmax = 14.5 ± 1.9 /mol/g prot/min。在 10% 胎牛血清 (FBS) 存在下，初始 Na 流入量与 [Na]o 的类似图给出了似乎是双相的非饱和曲线响应。血清依赖性 Na 内流与 [Na]o 的关系图（通过从存在 10% FBS 的曲线中减去不存在 FBS 时的曲线获得）显示，血清诱导的 Na 内流与外部 [Na] 之间存在线性关系。在生理钠浓度下，在存在胎牛血清的情况下，血清诱导的钠流入等于阿米洛利敏感的钠流入，而在不存在血清阿米洛利的情况下，抑制的钠流入小于10%。在测量 Na 通量之前，通过在含洋地黄毒苷的培养基中向细胞预载 Na 来测试细胞内 Na 对 Na 通量的影响。在没有血清的情况下，稳态 Na 交换通量与 [Na]o ([Na]i ≈︁ [Na]o) 的关系图给出了一条曲线，该曲线似乎在大约 100 mM Na 时达到饱和（通量 = 100 /μmol/g prot/min），然后随着 [Na] 的增加而下降（通量 = 40 /μmol/g prot/min，在 150 mM 时）。与对照血清剥夺细胞中的 Na 流入相反，负载 Na 的细胞中的 Na 流入因阿米洛利的存在而受到显着抑制。由于 100 μmol/g prot/min 的峰值 Na 交换通量大大超过对照血清剥夺细胞中 Na 流入的 Vmax，并且增强的 Na 通量是阿米洛利敏感的，因此升高细胞内 Na 必须以某种方式激活阿米洛利敏感的 Na 转运系统，该系统通常在没有血清的情况下仅具有最低限度的活性。
Sodium influx in serum‐deprived human fibroblasts is by way of a pathway which shows saturation kinetics. A plot of initial Na influx versus [Na]o ([Na]i = 10 mM) gives a simple Michaelis‐Menten type of curve with a K1/2 = 70.0 ± 8.1 mM and a Vmax = 14.5 ± 1.9 /mol/g prot/min. A similar plot of initial Na influx versus [Na]o in the presence of 10% fetal bovine serum (FBS) gives a nonsatu‐rating curvilinear response which appears to be biphasic. A plot of the serum‐dependent Na influx versus [Na]o (obtained by subtracting the curve in the absence of FBS from the curve in the presence of 10% FBS) shows that there is a linear relationship between serum‐induced Na influx and external [Na]. At physiological Na concentrations, in the presence of FBS, the serum‐induced Na influx is equal to the amiloride‐sensitive Na flux, whereas in the absence of serum amiloride inhibits less than 10% of the Na influx. The effect of intracellular Na on Na flux was tested by preloading cells with Na in a digitoxin‐containing medium prior to measurement of Na flux. A plot of steady‐state Na exchange flux versus [Na]o ([Na]i ≈︁ [Na]o) in the absence of serum gives a curve that appears to saturate at approximately 100 mM Na (flux = 100 /μmol/g prot/min) and then declines with increasing [Na] (flux = 40 /μmol/g prot/min at 150 mM). In contrast to Na influx in control serum‐deprived cells, Na flux in Na‐loaded cells is dramatically inhibited by the presence of amiloride. Since the peak Na exchange flux of 100 μmol/g prot/min is greatly in excess of the Vmax for Na influx in control serum‐deprived cells and the enhanced Na flux is amiloride‐sensitive, elevating intracellular Na must somehow activate the amiloride‐sensitive Na transport system, which is normally only minimally active in the absence of serum.