Hampton R Y, Holz R W
J Cell Biol. 1983 Apr;96(4):1082-8. doi: 10.1083/jcb.96.4.1082.
Recent evidence indicates that osmotic forces may play a role in exocytosis. To examine this possibility and to investigate the osmotic properties of storage granules within cells, we investigated the effects of changes of osmolality on stability and function of cultured bovine chromaffin cells. Cell volume measurements indicated that the cells behaved as osmometers and that the intracellular osmolality rapidly equilibrated with the osmolality of the extracellular medium. Hyperosmotic solutions strongly inhibited nicotinic agonist-stimulated secretion but did not alter nicotinic agonist-stimulated Ca(2+) uptake. Hyperosmotic solutions also strongly inhibited elevated potassium- stimulated secretion but only weakly inhibited elevated K(+)-stimulated Ca(2+) uptake. Thus, hyperosmotic solutions inhibited secretion at a step after calcium entry. Cells exposed to 165 mOs(1) solutions did not lyse and retained their capacity to store and secrete catecholamine upon stimulation. Significant intracellular lysis of chromaffin granules occurred within cells exposed to lower osmolalities. In contrast, 75 percent of the catecholamine was released from granules from cultured cells or from fresh adrenal medulla incubated in vitro at 210 mOs. The data provide evidence for a role for osmotic forces in exocytosis and suggest that if osmotic stress of the granule occurs during exocytosis, then water influx into chromaffin granules increases granule volume by at least 70 percent. The results also indicate that the osmotic properties of the granules are altered upon homogenization and subcellular fractionation of the cells.
最近的证据表明，渗透力可能在胞吐作用中发挥作用。为了研究这种可能性并探究细胞内储存颗粒的渗透特性，我们研究了渗透压变化对培养的牛嗜铬细胞稳定性和功能的影响。细胞体积测量表明，细胞表现为渗透计，细胞内渗透压与细胞外培养基的渗透压迅速达到平衡。高渗溶液强烈抑制烟碱激动剂刺激的分泌，但不改变烟碱激动剂刺激的Ca(2+)摄取。高渗溶液也强烈抑制高钾刺激的分泌，但仅微弱抑制高钾刺激的Ca(2+)摄取。因此，高渗溶液在钙进入后的一个步骤抑制分泌。暴露于165 mOs(1)溶液的细胞没有裂解，并在受到刺激时保留了储存和分泌儿茶酚胺的能力。在暴露于较低渗透压的细胞内发生了嗜铬颗粒的明显细胞内裂解。相反，75%的儿茶酚胺从培养细胞的颗粒中或从体外在210 mOs下孵育的新鲜肾上腺髓质中释放。这些数据为渗透力在胞吐作用中的作用提供了证据，并表明如果在胞吐作用期间颗粒发生渗透应激，那么水流入嗜铬颗粒会使颗粒体积增加至少70%。结果还表明，在细胞匀浆和亚细胞分级分离后，颗粒的渗透特性发生了改变。
