Pacini L, Spinedi A, Piacentini M, Limatola C, Farrace M G, Autuori F, Luly P
Department of Biology, University of Rome Tor Vergata, Italy.
Biochim Biophys Acta. 1990 Aug 6;1045(3):213-8. doi: 10.1016/0005-2760(90)90122-e.
Mouse keratinocytes cultured in a medium containing less than 0.1 mM Ca2+ (low Ca2+) incorporated [1-14C]arachidonic acid (AA) into phospholipids by kinetics including; (i) a rapid labelling of phosphatidylinositol (PtdIns), phosphatidylserine (PtdSer) and both acid-stable and alkenylacyl forms of phosphatidylcholine (PtdCho); and (ii) a slow but long-lasting radiolabel incorporation into both acid-stable and alkenylacyl forms of phosphatidylethanolamine (PtdEtn), partly associated with a net radioactivity loss from acid stable-PtdCho. Under low Ca2+ conditions no radioactivity transfer apparently occurred between PtdIns and other phospholipid classes. When cells were prelabelled for 24 h with [1-14C]AA and reincubated in label-free medium containing 1.2 mM Ca2+ (normal Ca2+), an early and extensive loss of radioactivity from PtdIns was observed, reasonably in connection with Ca2+ stimulation of phosphoinositide turnover. Cell shift to normal Ca2+ did not result in an increased synthesis of labelled eicosanoids, but was consistent with an increase of radioactivity incorporation into diacylglycerol (DAG) and with a complex pattern of [1-14C]AA redistribution, eventually leading to a marked radioactivity incorporation into acid stable-PtdEtn (but not into alkenylacyl-PtdEtn) and to a labelling decrease of acid stable-PtdCho. The possible mechanisms driving AA recycling after cell shift to normal Ca2+ are discussed.
在含有低于0.1 mM Ca2+（低钙）的培养基中培养的小鼠角质形成细胞，通过以下动力学过程将[1-14C]花生四烯酸（AA）掺入磷脂中：（i）快速标记磷脂酰肌醇（PtdIns）、磷脂酰丝氨酸（PtdSer）以及磷脂酰胆碱（PtdCho）的酸稳定形式和烯基酰基形式；（ii）缓慢但持久地将放射性标记掺入磷脂酰乙醇胺（PtdEtn）的酸稳定形式和烯基酰基形式，部分与酸稳定-PtdCho的净放射性损失相关。在低钙条件下，PtdIns与其他磷脂类别之间显然没有发生放射性转移。当细胞用[1-14C]AA预标记24小时，然后在含有1.2 mM Ca2+（正常钙）的无标记培养基中再孵育时，观察到PtdIns的放射性早期大量损失，这与Ca2+刺激磷酸肌醇周转合理相关。细胞转变为正常钙水平并未导致标记类花生酸合成增加，但与放射性掺入二酰基甘油（DAG）增加以及[1-14C]AA重新分布的复杂模式一致，最终导致大量放射性掺入酸稳定-PtdEtn（但不掺入烯基酰基-PtdEtn），并使酸稳定-PtdCho的标记减少。讨论了细胞转变为正常钙水平后驱动AA循环的可能机制。
