Fritschy W M, Wolters G H, van Schilfgaarde R
Department of Surgery, University of Groningen, Netherlands.
Diabetes. 1991 Jan;40(1):37-43. doi: 10.2337/diab.40.1.37.
We investigated the effect of alginate-polylysine-alginate microencapsulation on glucose-induced insulin secretion by rat islets. Applying the encapsulation method originally described by Lim, we found severely reduced in vitro insulin release (expressed as picomoles of insulin.10 islets-1.45 min-1 when incubated in 16.5 mM glucose), because the insulin release with encapsulated islets was 1.42 +/- 0.49 compared to 13.58 +/- 0.80 with free control islets. This could not be explained by inadequate permeability of the capsule, because insulin release was also severely reduced (2.12 +/- 0.61) when islets were subjected to the procedure but without the membrane-forming polylysine step. Therefore, islets were tested after having been subjected separately to each of the steps of the procedure. Insulin release was not affected by either alginate or CaCl2 but was severely reduced after prolonged suspension in saline or treatment with citrate. When saline and citrate were replaced by Ca2(+)-free Krebs-Ringer bicarbonate buffer (KRBB) and 1 mM EGTA, respectively, insulin release improved significantly both with complete and with incomplete (no polylysine step) encapsulation. This outcome was verified in a set of experiments run in parallel with islets derived from the same isolation procedure. Insulin release was 1.20 +/- 0.23 from islets encapsulated with the method of Lim and 10.73 +/- 1.04 from free control islets. With the modified procedure, insulin release was 9.17 +/- 0.52 vs. 9.61 +/- 1.27 for complete versus incomplete encapsulation, respectively. We conclude that Ca2(+)-free KRBB instead of saline and EGTA instead of citrate should be used to obtain an adequate insulin response from encapsulated islets and that the capsule membrane as such has no influence on glucose and insulin diffusion.
我们研究了海藻酸盐-聚赖氨酸-海藻酸盐微囊化对大鼠胰岛葡萄糖诱导胰岛素分泌的影响。应用Lim最初描述的包封方法，我们发现体外胰岛素释放严重减少（以胰岛素皮摩尔数表示。在16.5 mM葡萄糖中孵育时，10个胰岛-1.45分钟-1），因为与游离对照胰岛的13.58±0.80相比，包封胰岛的胰岛素释放为1.42±0.49。这不能用胶囊通透性不足来解释，因为当胰岛进行该程序但没有形成膜的聚赖氨酸步骤时，胰岛素释放也严重减少（2.12±0.61）。因此，在分别经历该程序的每个步骤后对胰岛进行测试。胰岛素释放不受海藻酸盐或CaCl2的影响，但在盐水中长时间悬浮或用柠檬酸盐处理后严重减少。当分别用无Ca2+的Krebs-Ringer碳酸氢盐缓冲液（KRBB）和1 mM EGTA代替盐水和柠檬酸盐时，无论是完全包封还是不完全包封（无聚赖氨酸步骤），胰岛素释放均显著改善。这一结果在与来自相同分离程序的胰岛平行进行的一组实验中得到了验证。用Lim方法包封的胰岛胰岛素释放为1.20±0.23，游离对照胰岛为10.73±1.04。采用改良程序时，完全包封和不完全包封的胰岛素释放分别为9.17±0.52和9.61±1.27。我们得出结论，应使用无Ca2+的KRBB代替盐水，EGTA代替柠檬酸盐，以从包封的胰岛中获得足够的胰岛素反应，并且胶囊膜本身对葡萄糖和胰岛素的扩散没有影响。
