热稳定型大肠杆菌肠毒素、茶碱和福斯高林对大鼠体内近端空肠中环核苷酸水平及黏膜表面（酸性微环境）pH的影响。

The effect of heat-stable Escherichia coli enterotoxin, theophylline and forskolin on cyclic nucleotide levels and mucosal surface (acid microclimate) pH in rat proximal jejunum in vivo.

作者信息

McKie A T, Kusel M, McEwan G T, Lucas M L

机构信息

Institute of Physiology, Glasgow University, U.K.

出版信息

Biochim Biophys Acta. 1988 Oct 7;971(3):325-31. doi: 10.1016/0167-4889(88)90148-6.

DOI:10.1016/0167-4889(88)90148-6

Abstract

The normally acidic mucosal surface pH of 6.24 +/- 0.02(30) in rat proximal jejunum in vivo is effectively neutralised by 30 min exposure to heat-stable Escherichia coli (STa) enterotoxin (14 micrograms/ml) to 6.80 +/- 0.07 (n = 5) or to a forskolin/theophylline combination (1 mM:20 mM) to 7.10 +/- 0.07(7) while perfusion with Krebs-phosphate buffer alone without glucose left the mucosal surface pH unchanged at a pH of 6.21 +/- 0.02(9). Forskolin alone had no effect, and 20 mM theophylline moderately elevated the surface pH to 6.52 +/- 0.03(5). Theophylline, forskolin and their combination all elevated cAMP levels per mg tissue DNA above control values while STa enterotoxin was without effect. In contrast, all agents elevated cGMP levels per mg tissue DNA above control levels. These findings indicate that surface pH is only moderately affected by changes in cAMP levels and is affected to a much greater extent by altered cGMP levels.

摘要

大鼠体内近端空肠黏膜表面正常的酸性pH值为6.24±0.02(30)，在体外用热稳定的大肠杆菌（STa）肠毒素（14微克/毫升）处理30分钟后，pH值有效中和至6.80±0.07（n = 5），或用福斯可林/茶碱组合（1毫摩尔/升:20毫摩尔/升）处理后pH值变为7.10±0.07(7)，而仅用不含葡萄糖的 Krebs - 磷酸盐缓冲液灌注时，黏膜表面pH值保持不变，为6.21±0.02(9)。单独使用福斯可林无作用，20毫摩尔/升的茶碱可使表面pH值适度升高至6.52±0.03(5)。茶碱、福斯可林及其组合均可使每毫克组织DNA中的cAMP水平高于对照值，而STa肠毒素则无此作用。相反，所有试剂均可使每毫克组织DNA中的cGMP水平高于对照水平。这些发现表明，表面pH值仅受到cAMP水平变化的适度影响，而受到cGMP水平变化的影响程度更大。