Tupper J T, Kaufman L, Bodine P V
J Cell Physiol. 1980 Jul;104(1):97-103. doi: 10.1002/jcp.1041040113.
Deprivation of extracellular Ca or serum inhibits the proliferation of WI38 human diploid fibroblasts. Under these conditions, the cells become quiescent at a point in the cell cycle typical of early G1 or G0 phase-arrested cells. Exit of the cells from this point in the cycle appears to require both the presence of serum and Ca simultaneously. If quiescent cells are serum-stimulated in low Ca medium (0.01 mM), they do not progress through G1 to the S phase, which normally requires 14-18 hr. However, they remain competent to do so. Addition of Ca for up to 48 hr after serum stimulation results in an equal fraction of the cells progressing G1 phase as compared to the presence of Ca at the time of serum addition. In contrast, if quiescent cells are serum-stimulated in the presence of Ca, which is then removed, the cells can remain competent to enter S phase for only 10-12 hr. Re-addition of Ca beyond this time does not allow G1 progression on a normal schedule. These data suggest that Ca and serum are both required to trigger, in whole or in part, the pleiotypic response. Ca appears also to render the cells competent to enter S phase, but this competence is labile; an observation consistent with the PDGF-induced competence observed previously in the 3T3 cell. These observations are in contrast to previous data from other cell types which suggest that Ca is required only in late G1 phase for successful entrance to S phase.
细胞外钙或血清的缺乏会抑制WI38人二倍体成纤维细胞的增殖。在这些条件下，细胞在细胞周期中处于典型的早期G1期或G0期停滞的点上进入静止状态。细胞从周期中的这一点退出似乎需要血清和钙同时存在。如果在低钙培养基（0.01 mM）中对静止细胞进行血清刺激，它们不会从G1期进展到S期，而这通常需要14 - 18小时。然而，它们仍然有这样做的能力。在血清刺激后添加钙长达48小时，与血清添加时存在钙相比，有相同比例的细胞进入G1期。相反，如果在有钙的情况下对静止细胞进行血清刺激，然后去除钙，细胞进入S期的能力只能维持10 - 12小时。超过这个时间重新添加钙并不能使细胞按正常进程进入G1期。这些数据表明，钙和血清都是触发全部或部分多型性反应所必需的。钙似乎也使细胞有进入S期的能力，但这种能力是不稳定的；这一观察结果与先前在3T3细胞中观察到的血小板衍生生长因子诱导的能力一致。这些观察结果与来自其他细胞类型的先前数据形成对比，那些数据表明钙仅在G1期后期才是成功进入S期所必需的。
