p1. Addition of extracellular pure pig brain calmodulin was found to modulate DNA synthesis and cell proliferation in K562 human leukaemic lymphocytes. At lower cell densities calmodulin significantly stimulated [3H]thymidine uptake; at higher densities it decreased it. 2. A protein biochemically indistinguishable from calmodulin was detected in the cell-conditioned media of rapidly dividing K562 cells. The concentration of calmodulin-like activity found in the conditioned media of these and a range of other normal and neoplastic cells (250-1636 ng/ml) was of the same order as would stimulate DNA synthesis in subconfluent cells. 3. Amounts of extracellular calmodulin-like activity and immunoreactivity varied during cell growth from low to high density, a peak of extracellular calmodulin preceding DNA synthesis in synchronized K562 cells. Extracellular calmodulin concentrations did not correlate with the presence of lactate dehydrogenase in the medium. 4. Inhibition of extracellular calmodulin activity by calmodulin antagonist immobilized on agarose beads, or by antibody to calmodulin, significantly decreased DNA synthesis. 5. These data strongly suggest that calmodulin or a very closely related protein can influence mitosis through an extracellular mechanism./p
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机译：> 1。发现添加细胞外纯猪脑钙调蛋白可调节K562人白血病淋巴细胞的DNA合成和细胞增殖。在较低的细胞密度下，钙调蛋白可显着刺激[3H]胸苷的摄取。在较高的密度下，它减少了。 2.在快速分裂的K562细胞的细胞条件培养基中检测到与钙调蛋白在生化上无法区分的蛋白质。在它们以及一系列其他正常和肿瘤细胞（250-1636 ng / ml）的条件培养基中发现的钙调蛋白样活性浓度与刺激亚融合细胞中DNA合成的浓度相同。 3.细胞生长过程中，细胞外钙调蛋白样活性和免疫反应性的数量从低到高变化，这是同步K562细胞中DNA合成之前的细胞外钙调蛋白的峰值。细胞外钙调蛋白浓度与培养基中乳酸脱氢酶的存在无关。 4.通过固定在琼脂糖珠上的钙调蛋白拮抗剂或钙调蛋白抗体抑制细胞外钙调蛋白活性，显着降低了DNA合成。 5.这些数据强烈表明钙调蛋白或一种密切相关的蛋白质可以通过细胞外机制影响有丝分裂。
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