锌诱导的蛋白合成增加可抵抗链佐霉素所致的胰岛细胞损伤

本工作在离体细胞水平观察ZnGl_2对链佐霉素(STZ)诱发的胰岛β细胞损伤的保护作用,并分析其可能的作用机制。结果如下:向培养的胰岛细胞中加入生理盐水和STZ(3mmol/L),孵育12h后,活细胞数由实验前的70万个/ml降至43.93±1.16万个/ml;将ZnCl_2(0.25、0.5、1.0mmol/L)和相同剂量的STZ一同加入细胞,可不同程度地缓解STZ对胰岛的破坏作用,在含不同浓度ZnCl_2的培养液中活细胞数分别恢复至47.39±0.88,58.06±2.29,67.72±1.48万个/ml,与STZ破坏组相比,分别具有显著差异,并呈量效关系。在给予ZnCl_2(1.0mmol/L)的同时,向细胞中加入蛋白合成抑制剂亚胺环已酮(100μg/ml),可翻转ZnCl_2的作用,活细胞数由63.17±2.15万个/ml,又重新减至45.77±0.76万个/ml。单独加亚胺环己酮对活细胞数目无明显影响。用~3H-亮氨酸掺入实验观察ZnCl_2对胰岛细胞蛋白合成的影响发现,单独给予ZnCl_2(1.0mmol/L)仅使蛋白合成轻微增加,与盐水对照组无显著差异;在给ZnCl_2的同时加入STZ,则蛋白合成明显增多,保护组与STZ破坏组比较,差异显著。上述结果表明,增加细胞内蛋白合成,以加强细胞自身对外来损伤的修复力,可能是ZnCl_2保护胰岛细胞的机制之一。

THE INCREASE OF PROTEIN SYNTHESIS BY ZINC CAN RESIST THE DAMAGE INDUCED BY STREPTOZOTOCIN ON ISLET CELLS

The beneficial effect of ZnCl2 on islet cells injured by streptozotocin was observed directly on the cultured cells and its possible mechanism was analysed. The results were as follows: (1) The number of viable cells in culture was reduced from 70 x 10(5)/ml to 43.93 +/- 1.16 x 10(5)/ml 12 hours after adding normal saline plus STZ (3.0 mmol/L), and this reduction could be alleviated by adding ZnCl2 (0.25, 0.5, 1.0 mmol/L) in varying amounts and a dose-response relationship was found. The number of viable cells was returned to 47.39 +/- 0.88 x 10(5)/ml, 58.06 +/- 2.29 x 10(5)/ml, and 67.72 +/- 1.48 x 10(5)/ml respectively in the culture with ZnCl2 of different levels. (2) The effect of ZnCl2 was reversed when cycloheximide (100 micrograms/ml), a protein synthesis inhibitor, was added into the cultural medium, and the number of viable cells was again decreased from 63.17 +/- 2.15 x 10(5)/ml to 45.77 +/- 0.76 x 10(5) ml. No obvious effect was observed when cycloheximide was given alone. (3) The experiment of 3H-leucine incorporation into islet cells showed that protein synthesis was increased slightly and insignificantly after adding ZnCl2 (1.0 mmol/L). However, there was a significant increase of protein synthesis in cells when ZnCl2 (1.0 mmol/L) was added with STZ (3.0 mmol/L). The results suggest that ZnCl2 has a protective effect on the damaged islet cells induced by STZ. The increase of protein synthesis may be one of the mechanisms involved in the action of ZnCl2, which strengthens the repairing ability of islet cells after injury.