Transport-coupling hypothesis of tubuloglomerular feedback signal transmission.
Transport-coupling hypothesis of tubuloglomerular feedback signal transmission.
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肾小球反馈信号传输的传输耦合假说。
DOI：
10.1152/ajprenal.1989.257.5.f882
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发表时间：
1989
期刊：
影响因子：
--
通讯作者：
Moore,LC
中科院分区：
文献类型：
--
作者：
Rich,A;Moore,LC
用一个数学模型探讨了肾小球旁结构(JGA)内致密黄斑(MD)向肾小球系膜外(EGM)传递信号的传递耦合假说。转运偶联假说认为，MD转运的变化改变了EGM间质的离子组成，从而刺激了Goormaghtigh细胞。这一假说是基于EGM的无血管，以及MD和Goormaghtigh细胞之间存在狭窄的裂隙(JGA裂隙)。该模型描述了MD细胞的氯化钠和水的运输以及JGA裂隙中的质量守恒。它计算裂隙水流量和氯化钠浓度[(氯化钠])。如果裂隙很窄，模型预测裂隙[氯化钠]将与管腔[氯化钠]和净MD-氯化钠的运输成正比。由于有很强的活性氯化钠转运，MD细胞斑块可能起到离子放大器的作用，因为管腔[氯化钠]的微小变化可能会在缝隙内引起大得多的浓度变化。即使没有主动的氯化钠转运，如果MD细胞被动地分泌氯化钠，裂隙[氯化钠]仍然可以与鲁米那[氯化钠]偶联。裂隙[氯化钠]具有很高的水力传导性，也会随着管腔渗透压的变化而变化。由于裂隙较宽，EGM间质的扩散阻力较低，或者MD侧方细胞间隙肿胀，裂隙与管腔[氯化钠]之间的转运耦合明显减弱。我们的模型预测的JGA间隙组成的巨大变化与在两栖动物上发表的测量结果吻合得很好。然而，哺乳动物MD的低Na+-K+-ATPase含量和高透水性表明，哺乳动物的转运偶联效应可能没有两栖类明显明显。
A mathematical model was used to explore the transport-coupling hypothesis of tubuloglomerular feedback (TGF) signal transmission from the macula densa (MD) to the extraglomerular mesangium (EGM) within the juxtaglomerular apparatus (JGA). The transport-coupling hypothesis supposes that changes in MD transport alter the ionic composition of the EGM interstitium, thereby stimulating the Goormaghtigh cells. This hypothesis is based on the avascularity of the EGM and the presence of a narrow cleft (JGA cleft) between the MD and Goormaghtigh cells. The model describes NaCl and water transport by MD cells and mass conservation in the JGA cleft. It calculates cleft water flow and NaCl concentration [( NaCl]). If the cleft is narrow, the model predicts that cleft [NaCl] will vary directly with luminal [NaCl] and net MD NaCl transport. With strong active NaCl transport, the MD cell plaque may act as an ionic amplifier, in that small changes in luminal [NaCl] might elicit much larger concentration changes within the cleft. Even without active NaCl transport, cleft [NaCl] could remain coupled to luminal [NaCl] if the MD cells passively secrete NaCl. With high hydraulic conductivity, cleft [NaCl] also varies with luminal osmolarity. With a wide cleft, a low diffusional resistance of the EGM interstitium, or swollen MD lateral intercellular spaces, the transport coupling between cleft and luminal [NaCl] is markedly attenuated. The predictions of our model of large changes in JGA interstitial composition agree well with published measurements made in Amphiuma. However, the low Na+-K+-ATPase content and high water permeability of mammalian MD suggest that the transport-coupling effects in mammals may be significantly less pronounced than in Amphiuma.