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

采用荧光显微镜和膜片钳技术分别测定正常成年大鼠和正常幼鼠胰腺B细胞胞内游离Ca^<2+>浓度（[Ca^<2+>]i）和膜电位。此外，我们还研究了交感神经系统去神经支配影响B细胞对药物反应的可能性。在部分刺激浓度的葡萄糖或甲磺丁酰胺存在的情况下，促进NO生成或增加细胞内环GMP含量的药物，如8-溴环GMP、人心房利钠肽、l -精氨酸、硝普钠、NOC 5和NOC 7，增加了正常成年大鼠分离的B细胞的[Ca^<2+>]i。在高浓度K^+的质膜去极化条件下，这些药物未能增加B细胞的[Ca^<2+>]i。[Ca^<2+>]i的增加被认为主要是由于Ca^<2+>通过质膜流入所致。在从正常幼鼠或交感神经切除的成年大鼠中分离的B细胞中，no -环gmp相关药物的作用与从正常成年大鼠分离的B细胞中观察到的相似。这些结果表明，在生理条件下，no -环GMP系统的激活积极调节胰腺B细胞胰岛素的释放。B细胞功能在衰老过程中可能发生的变化需要阐明。

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.