电生性阳离子跨水蛭盲肠上皮的转运

Electrogenic cation transport across leech caecal epithelium.

作者信息

Milde H, Clauss W, Weber W M

机构信息

Institute for Animal Physiology, Justus-Liebig-University Giessen, Germany.

出版信息

J Comp Physiol B. 1996;166(7):435-42. doi: 10.1007/BF02337888.

DOI:10.1007/BF02337888

PMID:8956504

Abstract

Electrogenic cation transport across the caecal epithelium of the leech Hirudo medicinalis was investigated using modified Ussing chambers. Transepithelial resistance (RT) and potential difference (VT) were 61.0 +/- 3.5 omega.cm2 and -1.1 +/- 0.2 mV (n = 149), respectively, indicating that leech caecal epithelium is a "leaky" epithelium. Under control conditions short circuit current (ISC) and transepithelial Na+ transport rate (INa) averaged at 22.1 +/- 1.5 microA.cm-2 and 49.7 +/- 2.6 microA.cm-2, respectively. Mucosal application of amiloride (100 mumol.l-1) or benzamil (50 mumol.l-1) influenced neither ISC nor INa. The transport system in the apical membrane showed no pronounced cation selectivity and a linear dependence on mucosal Na+ concentration. Removal of mucosal Ca2+ increased ISC by about 50% due to an increase of transepithelial Na+ transport. Trivalent cations (La3+ and Tb3+, 1 mmol.l-1 both) added to the mucosal Ringer solution reduced INa by more than 40%. Serosal ouabain (1 mmol.l-1) almost halved ISC and INa while 0.1% (= 5.4 mmol.l-1) DNP decreased INa to 11.8 +/- 5.1% of initial values. Serosal addition of cAMP increased both ISC and INa whereas the neurotransmitters. FMRFamide, acetylcholine, GABA, L-dopa, serotonin and dopamine failed to show any effects; octopamine, glycine and L-glutamate reduced INa markedly. On the basis of these results we conclude that in leech caecal epithelium apical uptake of monovalent cations is mediated by non-selective cation conductances which are sensitive to extracellular Ca2+ but insensitive to amiloride. Basolaterally Na+ is extruded via ouabain-sensitive and -insensitive ATPases. cAMP activates Na+ transport across leech caecal epithelium, although the physiological stimulus for cAMP-production remains unknown.

摘要

使用改良的尤斯灌流小室研究了电致阳离子跨药用水蛭盲肠上皮的转运。跨上皮电阻（RT）和电位差（VT）分别为61.0±3.5Ω·cm²和-1.1±0.2mV（n = 149），这表明水蛭盲肠上皮是一种“渗漏性”上皮。在对照条件下，短路电流（ISC）和跨上皮Na⁺转运速率（INa）平均分别为22.1±1.5μA·cm⁻²和49.7±2.6μA·cm⁻²。在黏膜侧施加氨氯地平（100μmol·L⁻¹）或苯甲酰咪（50μmol·L⁻¹）对ISC和INa均无影响。顶端膜中的转运系统未表现出明显的阳离子选择性，且对黏膜Na⁺浓度呈线性依赖。去除黏膜Ca²⁺由于跨上皮Na⁺转运增加使ISC升高约50%。添加到黏膜林格液中的三价阳离子（La³⁺和Tb³⁺，均为1mmol·L⁻¹）使INa降低超过40%。浆膜侧施加哇巴因（1mmol·L⁻¹）使ISC和INa几乎减半，而0.1%（=5.4mmol·L⁻¹）的二硝基苯酚（DNP）使INa降至初始值的11.8±5.1%。浆膜侧添加环磷酸腺苷（cAMP）使ISC和INa均增加，而神经递质苯甲酰酪胺、乙酰胆碱、γ-氨基丁酸（GABA）、左旋多巴、5-羟色胺和多巴胺未显示任何作用；章鱼胺、甘氨酸和L-谷氨酸显著降低INa。基于这些结果，我们得出结论，在水蛭盲肠上皮中，单价阳离子通过对细胞外Ca²⁺敏感但对氨氯地平不敏感的非选择性阳离子电导进行顶端摄取。在基底外侧，Na⁺通过对哇巴因敏感和不敏感的ATP酶排出。cAMP激活跨水蛭盲肠上皮的Na⁺转运，尽管cAMP产生的生理刺激仍不清楚。