Rabbit proximal colon: a distinct transport epithelium.
Rabbit proximal colon: a distinct transport epithelium.
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兔近端结肠：独特的运输上皮。
DOI：
10.1152/ajpgi.1984.246.5.g603
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发表时间：
1984
期刊：
影响因子：
--
通讯作者：
DeSoignie,R
中科院分区：
文献类型：
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作者：
Sellin,JH;DeSoignie,R
兔近端结肠（PC），体外检查，表现出不同于远端结肠的运输特征。与远端结肠不同，PC不表现出阿米洛利抑制电致钠吸收。此外，两性霉素和“刺激性”阴离子都不能诱导PC吸收Na。短路条件下的电测量和放射性同位素通量研究表明，PC是一种中等渗漏的上皮，电导（9.0 +/- 0.2 mS）介于回肠和远端结肠之间；在基本条件下，PC的Na和Cl输运速率接近于零，而5.5微米的肾上腺素（Epi）刺激电沉默的Na-Cl偶联吸收。我们进一步研究了这种共转运的机制：用硫酸盐或葡萄糖酸盐取代氯并没有实质性地改变外延素增强的Na吸收。Epi对无na溶液中Cl吸收的刺激减弱。Amiloride, 10(-3) M，抑制epi增强的Na吸收约50%。考察了camp介导的（茶碱或8-溴- camp）和ca介导的（离子载体A23187）分泌刺激的影响。在基态下，这些试剂对离子传输没有一致的影响。而Epi刺激Na和Cl吸收后，两种camp相关分泌物对Na和Cl转运均有明显的抗吸收作用。钙离子载体A23187的抗吸收作用不明显。这些结果表明，兔近端结肠a)不具有远端结肠的运输特性，b)具有epi敏感的na - cl偶联吸收途径，c)以抗吸收方式响应分泌刺激，而不是通过电致分泌。
Rabbit proximal colon (PC), examined in vitro, exhibits transport characteristics distinct from distal colon. Unlike distal colon, PC does not demonstrate amiloride-inhibitable electrogenic Na absorption. Additionally, neither amphotericin nor "stimulatory" anions induce Na absorption in PC. Electrical measurements and radioisotopic flux studies under short-circuit conditions indicate that PC is a moderately leaky epithelium with a conductance (9.0 +/- 0.2 mS) midway between ileum and distal colon; under basal conditions PC has Na and Cl transport rates near zero, and 5.5 microM epinephrine (Epi) stimulates electrically silent Na-Cl coupled absorption. The mechanism of this cotransport was investigated further: Cl substitution with either sulfate or gluconate did not substantially alter Epi-enhanced Na absorption. The Epi stimulation of Cl absorption in a Na-free solution was diminished. Amiloride, 10(-3) M, inhibited Epi-enhanced Na absorption by approximately 50%. The effects of cAMP-mediated (theophylline or 8-bromo-cAMP) and Ca-mediated (ionophore A23187) secretory stimuli were examined. In the basal state, none of these agents had a consistent effect on ion transport. However, after stimulation of Na and Cl absorption by Epi, both of the cAMP-related secretagogues had a marked antiabsorptive effect on Na and Cl transport. The antiabsorptive effects of Ca ionophore A23187 were less marked. These results suggest that rabbit proximal colon a) does not share the transport properties characteristic of distal colon, b) possesses an Epi-sensitive, Na-Cl-coupled absorptive pathway, and c) responds to secretory stimuli in an antiabsorptive manner rather than by electrogenic secretion.