Ion transport and electrophysiology of the early proximal colon of rabbit.
Ion transport and electrophysiology of the early proximal colon of rabbit.
复制标题
兔早期近端结肠的离子传输和电生理学。
DOI：
10.1007/bf00581161
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发表时间：
1987
期刊：
影响因子：
--
通讯作者：
Wills,NK
中科院分区：
文献类型：
--
作者：
Clauss,W;Biehler,KH;Schäfer,H;Wills,NK
在过去的十年里，哺乳动物降结肠的离子转运特性一直是众多研究的主题。相反，相对较少的研究对该器官的近段进行了研究。在本研究中，我们用放射性同位素示踪通量和电生理技术研究了Na+，K+和Cl-−在体外兔结肠起始段(P1)中的跨上皮转运。与兔降结肠一样，近端结肠主动吸收钠和氯，但其转运系统明显不同。在体内，该片段吸收钾，但在体外观察到活跃的钾分泌。与降结肠不同，Na+的吸收对阿米洛利相对不敏感，即使在1 mM的浓度下也只有轻微的抑制作用。Na+和Cl-−的吸收似乎是耦合的(直接或间接)，因为一个离子的吸收被另一个离子的去除所抑制。哇巴因还抑制Na+和Cl-−的吸收和净K+的分泌。与降结肠不同，近端的P1段没有在哇巴因存在下可检测到的净吸收K+转运系统。在电学上，早期近端结肠的跨上皮阻力低于降结肠(RT=133±7Ω/cm~2)，但短路电流较大(LSC=178±12μA/cm~2)。跨上皮电位平均为−21±1 mV，与活体测量值非常一致。根尖和基底侧膜电位分别为−21±1 mV和−42±1 mV，细胞内钾离子活度为70±2 mm。这些结果表明，主动的K+摄取跨越基底膜，而被动的K+穿过根尖膜。基侧膜电导可能是一种可被钡阻断的钾电导。正常情况下，钾离子的转运可能通过细胞和细胞旁两种途径发生。由于这一段与降结肠有许多不同，我们认为近端结肠的P1段在结肠电解质转运中具有明显的功能。
The ion transport properties of the mammalian descending colon have been the subject of numerous investigations during the last decade. In contrast, relatively few studies have investigated proximal segments of this organ. In the present study, we assessed transepithelial transport of Na+, K+and Cl−in the isolated initial segment (P1) of rabbit colon in vitro using radioisotopic tracer fluxes and electrophysiological techniques. Like the rabbit descending colon, the proximal colon actively absorbs sodium and chloride, howeveer, its transport systems are markedly different. In vivo, this segment absorbs potassium, however in vitro active potassium secretion was observed. Unlike the descending colon, Na+absorption is relatively insensitive to amiloride and only a slight inhibition was obtained even at 1 mM concentrations of this drug. Na+and Cl−absorption appeared to be coupled (directly or indicrectly) since the absorption of each ion was inhibited by the removal of the other. Serosal ouabain also inhibited Na+and Cl−absorption and net K+secretion. Unlike the descending colon, the proximal P1 segment did not have a net absorptive K+transport system that was detectable in the presence of ouabain. Electrically, the early proximal colon has a low transepithelial resistance compared to descending colon (RT=133±7 Ω cm2) but a larger short-circuit current (lsc=178±12 μA/cm2). The transepithelial potential averaged −21±1 mV, in excellent agreement with values measured in vivo. The apical and basolateral membrane potentials averaged −21±1 mV and −42±1 mV and intracellular potassium activity was 70±2 mM. The findings indicate active K+uptake across the basolateral membrane and passive exit across the apical membrane. The basolateral membrane conductance may be a potassium conductance that is blockable by barium. It is likely that K+transport normally occurs by both cellular and paracellular routes in this epithelium. Because of the numerous differences between this segment and the descending colon, we conclude that the P1 segment of proximal colon has a distinct function in colonic electrolyte transport