Studies on changes in the pancreatic B cell function during development and aging assessed by computer-aided fluorescent microscopy

在分离的正常成年和幼年大鼠胰腺B细胞中，分别用Fura 2荧光显微镜和膜片钳技术测定细胞内游离钙离子浓度([Ca^lt；2+gt；]i)和膜电位。在部分刺激浓度的葡萄糖或甲苯丁胺存在的情况下，促进NO产生或增加细胞内环GMP含量的药物，如8-溴-环鸟苷、人心钠素、L-精氨酸钠、硝普钠、NOC5和NOC7，均可使正常成年大鼠分离的B细胞[Ca~(2+)~(2+)]~(2+)升高。在含有高浓度K~(++)的质膜去极化条件下检测B细胞。细胞内[Ca~(2+)]i的升高可能主要是由于Ca~(2+)通过质膜内流所致。在正常幼鼠和去交感神经的成年大鼠分离的B细胞中，NO-环状GMP相关药物的作用与从正常成年大鼠分离的B细胞的作用相似。这些结果表明，在生理条件下，NO-环状GMP系统的激活正向延髓了胰腺B细胞的胰岛素释放。衰老过程中B细胞功能的可能变化需要阐明。

In pancreatic B cells isolated from normal adult and normal young rats, the intracellular free Ca^<2+> concentration ([Ca^<2+>]i) and the membrane potential were measured by fluorescent microscopy using fura 2 and patch clamp technique, respectively. Furthermore, the possibility that denervation of the sympathetic nervous system affects responsiveness of B cells to drugs was examined.In the presence of partially stimulating concentrations of glucose or tolbutamide, agents that facilitate NO production or augment intracellular cyclic GMP content, such as 8-bromo-cyclic GMP,human atrial natriuretic peptide, L-arginine, sodium nitroprusside, NOC 5 and NOC 7, increased [Ca^<2+>]i of B cells isolated from normal adult rats, as observed with cyclic AMP.However, these agents failed to increase [Ca^<2+>]i of B cells when tested under depolarization of the plasma membrane with high concentrations of K^+. The increase in [Ca^<2+>]i was considered to be mainly due to Ca^<2+> influx through the plasma membrane. In the case of B cells isolated from normal young or sympathectomized adult rats, effects of the NO-cyclic GMP-related agents were similar to those observed with B cells isolated from normal adult rats.These results suggest that activation of the NO-cyclic GMP system positively medullates the release of insulin from pancreatic B cells under the physiological conditions. Possible changes in the B cell function during aging need to be elucidated.