Harel L, Blat C, Chatelain G
J Cell Physiol. 1985 Apr;123(1):139-43. doi: 10.1002/jcp.1041230120.
The growth rate of normal cells multiplied in vitro decreases as the cell density of the culture increases. Previous results suggested that this density-dependent inhibition of growth in nontransformed cells was due to the diffusion of growth inhibitory substances in the medium of dense cultures. In this paper, we demonstrate that dense cultures of 3T3 cells secrete inhibitory and stimulatory factors. Macromolecules of conditioned medium were fractionated on Biogel P150 and the different fractions were tested on quiescent cultures of 3T3 cells stimulated or not to proliferate by addition of alpha globulin. When target cells were not stimulated to proliferate by addition of exocrine growth factors, we observed the inhibitory activity of a large molecular weight inhibitor (IDF45) and the stimulatory activity of autocrine growth factors (fraction about 35 and 10 K molecular weight), on the incorporation of 14C inosine into nucleotide pool and RNA. However, DNA synthesis was significantly stimulated with fraction 10 K only. This discrepancy between the stimulation of RNA and DNA synthesis may be explained by the presence, simultaneously, of inhibitory and stimulatory factors in fraction 35 and 10 K molecular weight. The presence of inhibitory factor was demonstrated when the fractions were tested on target cells stimulated to proliferate by alpha globulin addition and labeled with 14C thymidine. In these conditions, the stimulatory activity of autocrine growth factors was not observable, and only the inhibitory activity on DNA synthesis of fractions 35 and 10 K appeared. It is tempting to assume that the regulation of in vitro cell proliferation is determined by the balance between these antagonist stimulatory and inhibitory autocrine growth factors.
体外培养的正常细胞的生长速率会随着培养物细胞密度的增加而降低。先前的结果表明，这种非转化细胞中依赖密度的生长抑制是由于密集培养物培养基中生长抑制物质的扩散所致。在本文中，我们证明3T3细胞的密集培养物会分泌抑制性和刺激性因子。条件培养基的大分子在Biogel P150上进行分级分离，不同级分在添加α球蛋白刺激或未刺激增殖的3T3细胞静止培养物上进行测试。当通过添加外分泌生长因子未刺激靶细胞增殖时，我们观察到一种大分子抑制剂（IDF45）的抑制活性以及自分泌生长因子（约35和10K分子量级分）对14C次黄苷掺入核苷酸池和RNA的刺激活性。然而，只有10K级分能显著刺激DNA合成。RNA和DNA合成刺激之间的这种差异可能是由于35和10K分子量级分中同时存在抑制性和刺激性因子所致。当这些级分在通过添加α球蛋白刺激增殖并用14C胸苷标记的靶细胞上进行测试时，证明了抑制因子的存在。在这些条件下，未观察到自分泌生长因子的刺激活性，仅出现35和10K级分对DNA合成的抑制活性。很诱人的推测是，体外细胞增殖的调节是由这些拮抗性的刺激性和抑制性自分泌生长因子之间的平衡所决定的。
