Polgreen K E, Kemp G J, Leighton B, Radda G K
Department of Biochemistry, University of Oxford, UK.
Biochim Biophys Acta. 1994 Sep 8;1223(2):279-84. doi: 10.1016/0167-4889(94)90238-0.
In vivo, skeletal muscle Pi uptake influences both muscle cellular [Pi] and plasma [Pi], and may mediate the hypophosphataemic effects of insulin and insulin-like growth factor 1 (IGF-1). These effects were investigated in the cultured mouse myoblast cell line G8 and the isolated incubated rat soleus. The low Km for Pi in G8 cells is consistent with in vivo evidence that muscle cell [Pi] is partially protected against changes in plasma [Pi]. Insulin and IGF-1 stimulated Na-dependent Pi influx: in G8 cells both increased Vmax, with no change in Km, but while the insulin response occurred within 15 min and rapidly reversed upon insulin withdrawal, the response to IGF-1 occurred only after 60 min and persisted at least 60 min following IGF-1 withdrawal. Furthermore, only the IGF-1 response was inhibited by cycloheximide. We suggest that IGF-1 operates through de novo protein synthesis, while insulin stimulates transporter recruitment to the cell surface.
在体内，骨骼肌对无机磷酸盐（Pi）的摄取会影响肌肉细胞内的[Pi]以及血浆中的[Pi]，并且可能介导胰岛素和胰岛素样生长因子1（IGF - 1）的低磷血症效应。在培养的小鼠成肌细胞系G8和分离并孵育的大鼠比目鱼肌中对这些效应进行了研究。G8细胞中Pi的低米氏常数（Km）与体内证据一致，即肌肉细胞内的[Pi]在一定程度上可免受血浆[Pi]变化的影响。胰岛素和IGF - 1刺激了钠依赖性Pi内流：在G8细胞中，二者均增加了最大反应速度（Vmax），而米氏常数（Km）不变，但胰岛素反应在15分钟内发生，且在撤除胰岛素后迅速逆转，而对IGF - 1的反应仅在60分钟后出现，并在撤除IGF - 1后至少持续60分钟。此外，只有IGF - 1的反应受到放线菌酮的抑制。我们认为，IGF - 1通过从头合成蛋白质发挥作用，而胰岛素则刺激转运体募集到细胞表面。
