Deleers M, Lebrun P, Malaisse W J
Horm Metab Res. 1985 Aug;17(8):391-5. doi: 10.1055/s-2007-1013555.
Fluorescein rapidly accumulates in rat pancreatic islets exposed to fluorescein diacetate. The influence of environmental agents upon cellular pH was examined in fluorescein-labelled islets by recording their fluorescence intensity at 520 nm after excitation at 490 and 435 nm, respectively. Glucose caused a rapid, sustained and dose-related increase in cellular pH. Another nutrient secretagogue, 2-ketoisocaproic acid, also increased cellular pH. The stimulation of islet cells by non-nutrient secretagogues, e.g. by glibenclamide or in response to an increase in extracellular K+ concentration, decreased cellular pH, indicating that the nutrient-induced increase in cellular pH is not merely a consequence of stimulated Ca2+ inflow and/or insulin release. In either the presence of amiloride or absence of bicarbonate, glucose decreased cellular pH. These results strongly suggest that the acidification of islet cells which can be expected from the increased metabolism of glucose in glucose-stimulated islets is normally masked and overcome by stimulation of such processes as Na+/H+ and HCO3-/Cl- exchange.
荧光素会迅速在暴露于二乙酸荧光素的大鼠胰岛中积累。通过分别在490纳米和435纳米激发后记录荧光素标记的胰岛在520纳米处的荧光强度，研究了环境因素对细胞pH值的影响。葡萄糖导致细胞pH值迅速、持续且呈剂量相关的升高。另一种营养性促分泌剂2-酮异己酸也会使细胞pH值升高。非营养性促分泌剂（如格列本脲）刺激胰岛细胞或细胞外钾离子浓度升高时，细胞pH值会降低，这表明营养物质诱导的细胞pH值升高不仅仅是刺激钙内流和/或胰岛素释放的结果。在存在氨氯吡咪或不存在碳酸氢盐的情况下，葡萄糖都会降低细胞pH值。这些结果有力地表明，在葡萄糖刺激的胰岛中，由于葡萄糖代谢增加而预期的胰岛细胞酸化通常会被诸如钠/氢和碳酸氢根/氯交换等过程的刺激所掩盖和克服。
