Zachayus J L, Plas C
Laboratoire de Biologie-Odontologie, Université Paris 7, Institut Biomédical des Cordeliers, France.
J Cell Physiol. 1995 Mar;162(3):330-40. doi: 10.1002/jcp.1041620305.
The effects of a mild heat shock were investigated using cultured 15-day-old fetal rat hepatocytes in which an acute glucocorticoid-dependent glycogenic response to insulin was present. After exposure from 15 min to 2 h at 42.5 degrees C, cell surface [125I]insulin binding progressively decreased down to 60% of the value shown in cells kept at 37 degrees C, due toa decrease in the apparent number of insulin binding sites with little change in insulin receptor affinity. In parallel cultures, protein labeling with [35S]methionine exhibited stimulated synthesis of specific proteins, in particular, 73-kDa Hsc (heat shock cognate) and 72-kDa Hsp (heat shock protein). When cells were returned to 37 degrees C after 2 h at 42.5 degrees C, cell surface insulin binding showed a two-third restoration within 3 h (insulin receptor half-life = 13 h), with similar concomitant return of Hsps72,73 synthesis to preinduction levels. The rate of [14C]glucose incorporation into glycogen measured at 37 degrees C after 1- to 2-h heat treatment revealed a striking yet transient increase in basal glycogenesis (up to 5-fold). At the same time, the glycogenesis stimulation by insulin was reduced (from 3.2 to 1.4-fold), whereas that induced by a glucose load was maintained. Induction of thermotolerance after a first heating was obtained for the heat shock-dependent events except for the enhanced basal glycogenesis. In insulin-unresponsive cells grown in the absence of glucocorticoids, heat shock decreased the glycogenic capacity without modifying the glucose load stimulation, supporting the hypothesis that insulin and thermal stimulation of glycogenesis share at least part of the same pathway. Inverse variations were observed between Hsps72,73 synthesis and both cell surface insulin receptor level and insulin glycogenic response in fetal hepatocytes experiencing heat stress.
利用培养的15日龄胎鼠肝细胞研究了轻度热休克的影响，这些肝细胞存在对胰岛素的急性糖皮质激素依赖性糖原生成反应。在42.5℃下暴露15分钟至2小时后，细胞表面[125I]胰岛素结合逐渐减少，降至37℃下培养细胞所显示值的60%，这是由于胰岛素结合位点的表观数量减少，而胰岛素受体亲和力变化不大。在平行培养中，用[35S]甲硫氨酸进行蛋白质标记显示特定蛋白质的合成受到刺激，特别是73-kDa热休克同源蛋白（Hsc）和72-kDa热休克蛋白（Hsp）。当细胞在42.5℃下培养2小时后再回到37℃时，细胞表面胰岛素结合在3小时内恢复了三分之二（胰岛素受体半衰期=13小时），同时Hsps72、73的合成也恢复到诱导前水平。在1至2小时热处理后于37℃下测量的[14C]葡萄糖掺入糖原的速率显示基础糖原生成有显著但短暂的增加（高达5倍）。同时，胰岛素对糖原生成的刺激作用减弱（从3.2倍降至1.4倍），而葡萄糖负荷诱导的糖原生成作用保持不变。除了基础糖原生成增强外，首次加热后对热休克依赖性事件诱导出了热耐受性。在无糖皮质激素条件下生长的胰岛素无反应细胞中，热休克降低了糖原生成能力，而不改变葡萄糖负荷刺激，这支持了胰岛素和糖原生成的热刺激至少部分共享同一途径的假说。在经历热应激的胎肝细胞中，观察到Hsps72、73合成与细胞表面胰岛素受体水平及胰岛素糖原生成反应之间呈反向变化。
