电生性钠转运通过水蛭皮肤的调节。

Regulation of electrogenic Na+ transport across leech skin.

作者信息

Weber W M, Blank U, Clauss W

机构信息

Institut für Tierphysiologie, Justus-Liebig-Universität Giessen, Germany.

出版信息

Am J Physiol. 1995 Mar;268(3 Pt 2):R605-13. doi: 10.1152/ajpregu.1995.268.3.R605.

DOI:10.1152/ajpregu.1995.268.3.R605

PMID:7900902

Abstract

The dorsal integument of the medical leech Hirudo medicinalis exhibits a marked amiloride-sensitive Na+ absorption. With 20 mM Na+ in the apical solution, the transepithelial short-circuit current (Isc) was approximately 40% higher than with 115 mM Na+, whereas the transepithelial potential (VT) with 20 mM Na+ was -35.7 +/- 4.5 and -20.6 +/- 2.6 mV with 115 mM Na+. Amiloride (100 microM) inhibition at 20 mM apical Na+ was also significantly larger than with 115 mM Na+ in the solution. Benzamil (100 microM) showed additional inhibition after amiloride. Large transient overshooting currents occurred only when 115 mM Na+ was added after some minutes of Na(+)-free apical solution. Addition of adenosine 3',5'-cyclic monophosphate (cAMP) to the serosal side in the presence of 115 mM apical Na+ nearly doubled Isc. This cAMP effect was reduced to only 20% in the presence of 20 mM Na+. Guanosine 3',5'-cyclic monophosphate (cGMP) slightly increased Isc, whereas ATP showed biphasic potency. Removal of calcium from the apical side resulted in a large stimulation of amiloride-sensitive Isc only in the presence of 115 mM Na+. When currents were activated with cAMP, a deprivation of Ca2+ modestly reduced the amiloride-sensitive Isc. The Na+ channel of leech integument was found highly selective for Na+ over other monovalent cations. The permeability ratio for Na+ over K+ was approximately 30:1; the selectivity relationship for the investigated cations was Na+ > Li+ > NH4+ > K+ approximately Cs+ approximately Rb+.

摘要

医用水蛭（Hirudo medicinalis）的背部体表呈现出显著的对氨氯吡脒敏感的Na⁺吸收。在顶端溶液中含有20 mM Na⁺时，跨上皮短路电流（Isc）比含有115 mM Na⁺时大约高40%，而含有20 mM Na⁺时的跨上皮电位（VT）为-35.7±4.5 mV，含有115 mM Na⁺时为-20.6±2.6 mV。在顶端20 mM Na⁺时，氨氯吡脒（100 μM）的抑制作用也明显大于溶液中含有115 mM Na⁺时。苯扎米（100 μM）在氨氯吡脒之后显示出额外的抑制作用。仅在无Na⁺的顶端溶液处理几分钟后加入115 mM Na⁺时，才会出现大的瞬时过冲电流。在顶端含有115 mM Na⁺的情况下，向浆膜侧添加腺苷3',5'-环磷酸（cAMP）使Isc几乎增加了一倍。在含有20 mM Na⁺的情况下，这种cAMP效应仅降至20%。鸟苷3',5'-环磷酸（cGMP）使Isc略有增加，而ATP表现出双相效力。仅在含有115 mM Na⁺的情况下，从顶端侧去除钙会导致对氨氯吡脒敏感的Isc大幅增加。当用cAMP激活电流时，去除Ca²⁺会适度降低对氨氯吡脒敏感的Isc。发现水蛭体表的Na⁺通道对Na⁺的选择性远高于其他单价阳离子。Na⁺对K⁺的渗透比约为30:1；所研究阳离子的选择性关系为Na⁺>Li⁺>NH₄⁺>K⁺≈Cs⁺≈Rb⁺。