McKay J S, Linaker B D, Turnberg L A
Gastroenterology. 1981 Feb;80(2):279-84.
Opiates are commonly used as antidiarrheal agents, and endogenous opioids have been demonstrated in the intestine. It seemed important therefore to investigate the effects of morphine on ion transport across intestinal mucosa. In rabbit ileum in vitro morphine (2 x 10(-5) M) induced a significant fall in potential difference and short circuit current but did not influence tissue resistance. Dextromoramide (10(-5) M), an active opiate, mimicked the action of morphine, whereas the inactive isomer levomoramide (10(-5) M) had no effect. Morphine caused a significant increase in chloride absorption, due predominantly to a decrease in the serosa to mucosa flux. No change in sodium transport was detected, but the residual ion flux, possibly representing bicarbonate secretion, was enhanced. Similar response were observed with a synthetic enkephalin analogue (Me-Tyr-D-Met-Gly-Phe-Pro-NH2); but this was more potent than morphine, a significant electrical response being observed at a concentration as low as 10(-8) M. These electrical and ion transport responses to morphine were blocked by naloxone, an effect shown to be competitive in nature. The results suggest that opiate receptors exist in rabbit ileal mucosa and that these influence electrical and ion transport changes across the mucosa.
阿片类药物通常用作止泻剂，并且已在肠道中证实存在内源性阿片样物质。因此，研究吗啡对跨肠黏膜离子转运的影响似乎很重要。在体外兔回肠中，吗啡（2×10⁻⁵M）导致电位差和短路电流显著下降，但不影响组织电阻。活性阿片类药物右吗拉胺（10⁻⁵M）模拟了吗啡的作用，而无活性的异构体左吗拉胺（10⁻⁵M）则无作用。吗啡导致氯离子吸收显著增加，主要是由于浆膜到黏膜的通量减少。未检测到钠转运的变化，但可能代表碳酸氢盐分泌的残余离子通量增加。用一种合成脑啡肽类似物（Me-Tyr-D-Met-Gly-Phe-Pro-NH₂）观察到类似反应；但它比吗啡更有效，在低至10⁻⁸M的浓度下就观察到了显著的电反应。这些对吗啡的电和离子转运反应被纳洛酮阻断，结果表明这种作用具有竞争性。结果表明，兔回肠黏膜中存在阿片受体，并且这些受体影响跨黏膜的电和离子转运变化。
