Tantisira M H, Jodal M, Lundgren O
Dept. of Physiology, Gothenburg University, Sweden.
Scand J Gastroenterol. 1990 Jan;25(1):19-28. doi: 10.3109/00365529008999205.
The effects of the heat-stable enterotoxin of Escherichia coli (STa) on intestinal alkaline secretion and transepithelial electric potential difference (PD) were investigated in vivo in denervated segments of rat jejunum, ileum, and proximal colon. STa caused a significant increase in alkaline secretion in the jejunum but not in the ileum or colon. The jejunal effect of STa may be ascribed to a stimulation of bicarbonate secretion and/or an inhibition of Na+/H+ exchange. With regard to PD, STa caused a marked rise in colonic PD, whereas only a small response was found in the jejunum. No effect on PD was seen in the ileum. Hexamethonium (10 mg/kg intravenously) significantly diminished the effects of STa on PD, whereas only a small inhibition of the STa-induced alkaline secretion was observed. The effect of lidocaine on PD and alkaline secretion was found to be similar to that of hexamethonium. Atropine had no effect on any of the studied variables. These findings suggest that STa exerts, via nerves, a profound influence on the jejunal transport mechanisms responsible for the changes in PD, whereas the influence on alkaline secretion is to a large extent not mediated via enteric nerves. Thus, the extent of enteric nervous control of epithelial function differs for different transport functions. The findings also indicate that the bicarbonate ion is not the anion mainly responsible for the fluid secretion elicited by STa.
在大鼠空肠、回肠和近端结肠的去神经节段中，研究了大肠杆菌热稳定肠毒素（STa）对肠道碱性分泌和跨上皮电位差（PD）的影响。STa可使空肠中的碱性分泌显著增加，但对回肠或结肠无此作用。STa对空肠的作用可能归因于刺激碳酸氢盐分泌和/或抑制Na+/H+交换。关于PD，STa可使结肠PD显著升高，而在空肠中仅发现微小反应。在回肠中未观察到对PD的影响。六甲铵（静脉注射10mg/kg）可显著减弱STa对PD的作用，而仅观察到对STa诱导的碱性分泌有轻微抑制。发现利多卡因对PD和碱性分泌的作用与六甲铵相似。阿托品对任何研究变量均无影响。这些发现表明，STa通过神经对负责PD变化的空肠转运机制产生深远影响，而对碱性分泌的影响在很大程度上不是通过肠神经介导的。因此，肠道神经对上皮功能的控制程度因不同的转运功能而异。研究结果还表明，碳酸氢根离子不是STa引起液体分泌的主要阴离子。
