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

分离正常成年和正常青年大鼠胰腺B细胞，分别用荧光显微镜和膜片钳技术测定细胞内游离Ca^<2 +>浓度（[Ca^<2+]i）和膜电位。在部分刺激浓度的葡萄糖或甲苯磺丁脲存在下，促进NO产生或增加细胞内环GMP含量的药物，如8-溴-环GMP，人心房钠尿肽，L-精氨酸，硝普钠，NOC 5和NOC 7，用环磷酸腺苷（cAMP）可增加正常成年大鼠B细胞的[Ca^<2+>]i，但在高浓度K^+的质膜去极化条件下，这些药物不能增加B细胞的[Ca^<2+>]i。[Ca^<2+>]i的增加被认为主要是由于Ca^<2+>通过质膜内流。在正常青年或交感神经切除成年大鼠分离的B细胞的情况下，NO-环GMP相关剂的作用与从正常成年大鼠分离的B细胞观察到的作用相似。这些结果表明，NO-环GMP系统的激活积极地促进了生理条件下胰腺B细胞的胰岛素释放。需要阐明衰老过程中B细胞功能可能发生的变化。

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.