Eckel R H, Fujimoto W Y, Brunzell J D
Int J Obes. 1981;5(6):571-7.
The synthesis and secretion of lipoprotein lipase activity is one marker of the adipocyte state in cultured 3T3-L1 cells. Lipoprotein lipase in these cells is responsive to hormones (insulin and GIP); however, this has not been a constant feature. To determine if in-vitro lifespan or passage number contributes to this responsiveness, cells over an in-vitro lifespan of nine to 22 passages were examined for insulin- and GIP-mediated increases in enzyme synthesis and secretion. Differences in GIP responsiveness between the parent line and 3T3-L1 subclones were also tested. Insulin-mediated release of lipase into the culture medium (P less than 0.02) and the stimulation of heparin-releasable activity from cells by insulin (P less than 0.05) were inversely related to passage number. The responsiveness to GIP also decreased with increasing in-vitro lifespan. Differences between the parent cell and subclones were also seen for GIP. The loss of responsiveness in these cells appears to be associated with an increase in confluent density. There was no relationship between basal lipoprotein lipase activity and passage number. Therefore, the effect of insulin and GIP on lipoprotein lipase activity in 3T3-L1 cells is not a stable property and some caution is required before applying data obtained from these cells to the in-vivo situation.
脂蛋白脂肪酶活性的合成与分泌是培养的3T3-L1细胞中脂肪细胞状态的一个标志。这些细胞中的脂蛋白脂肪酶对激素（胰岛素和胃抑肽）有反应；然而，这并非一直如此。为了确定体外寿命或传代次数是否对这种反应性有影响，研究了体外传代9至22代的细胞中胰岛素和胃抑肽介导的酶合成与分泌的增加情况。还测试了亲代细胞系和3T3-L1亚克隆之间对胃抑肽反应性的差异。胰岛素介导的脂肪酶释放到培养基中的量（P<0.02）以及胰岛素对细胞中肝素可释放活性的刺激（P<0.05）与传代次数呈负相关。对胃抑肽的反应性也随着体外寿命的增加而降低。在胃抑肽方面，亲代细胞与亚克隆之间也存在差异。这些细胞反应性的丧失似乎与汇合密度的增加有关。基础脂蛋白脂肪酶活性与传代次数之间没有关系。因此，胰岛素和胃抑肽对3T3-L1细胞中脂蛋白脂肪酶活性的影响不是一个稳定的特性，在将从这些细胞获得的数据应用于体内情况之前需要谨慎。
