PGF_(2α)对NIT-1β细胞葡萄糖刺激性胰岛素分泌的影响

目的探讨PGF2α对葡萄糖刺激性胰岛素分泌和[Ca2+]i变化的影响。方法运用放免方法检测不同浓度的PGF2α在不同情况下对NIT-1β细胞葡萄糖刺激性胰岛素分泌量的变化,并以F luo-3AM为探针,利用激光共聚焦显微镜检测细胞内钙的改变。结果在16.5 mmol.L-1葡萄糖刺激下,0.1、1、5μmol.L-1的PGF2α剂量依赖性的促进了NIT-1β细胞葡萄糖刺激性胰岛素分泌,其中5μmol.L-1时作用最强(P<0.01),而在10μmol.L-1时,PGF2α却抑制了葡萄糖刺激的胰岛素分泌(P<0.05);预先加入0.5 mmol.L-1EGTA后,5μmol.L-1的PGF2α不能促进胰岛素分泌,同样在预先加入n ifed ip ine或EGTA+n ifed ip ine后,PGF2α也无促进胰岛素分泌(P>0.05)。在0、5.5 mmol.L-1葡萄糖刺激下,5μmol.L-1的PGF2α无促进胰岛素分泌作用(P>0.05)。另外,应用5μmol.L-1的PGF2α能够引起β细胞内钙升高(P<0.01),在无钙环境下,PGF2α只引起缓慢的幅度较小的细胞内钙升高,恢复细胞外钙浓度时,β细胞内钙升高(P<0.01)。结论在NIT-1β细胞,一定范围浓度的PGF2α能够促进高浓度葡萄糖刺激下的胰岛素分泌,可能与PGF2α增加细胞外钙内流有关。

Effects of PGF2α on the glucose-stimulated insulin secretion in NIT-1 beta cells

Aim To investigate the effects of PGF_(2α) upon glucose-stimulated insulin secretion and the calcium response in NIT-1 beta cells.Methods Using the radioimmunoassay(RIA),the amount of PGF_(2α) augmentation of glucose-stimulated insulin secretion was determined in different conditions and the confocal laser scanning methods by Fluo-3AM as a fluorescent probe were used to analyze the NIT-1 beta cell intracellular calcium response in correlated various terms.Results In the presence of 16.5 mmol·L~(-1) glucose,PGF_(2α)(0.1,1,5 μmol·L~(-1)) dose-dependently augmented glucose-induced insulin secretion in NIT-1 beta cells,especially at 5 μmol·L~(-1)(P<0.01);whereas the higher concentration(10 μmol·L~(-1)) of PGF_(2α) even tended to suppress the insulin release(P<0.05);in the presence of EGTA or/and nifedipine,PGF_(2α)(5 μmol·L~(-1)) was no longer able to potentiate glucose(16.5 mmol·L~(-1))-induced insulin secretion.At the lower glucose(0,5.5 mmol·L~(-1)),PGF_(2α)(5 μmol·L~(-1)) failed to potentiate insulin secretion(P>0.05).Meanwhile,Exposure of the NIT-1 cells to 5 μmol·L~(-1) PGF_(2α) induced a rapid increase of intracellular calcium(P<0.01);however,in the absence of extracellular calcium,the cells responded to PGF_(2α) with a small,prolonged elevation of intracellular calcium that increased significantly when extracellular calcium was replenished(P<0.01).Conclusion PGF_(2α) in a limited concentration range,potentiates higher concentration glucose-induced insulin secretion in NIT-1 beta cells through promotion extracellular Ca~(2+) entry.