Salomonsson M, Gonzalez E, Westerlund P, Persson A E
Department of Physiology and Biophysics, University of Lund, Sweden.
Acta Physiol Scand. 1991 Jun;142(2):283-90. doi: 10.1111/j.1748-1716.1991.tb09158.x.
The juxtaglomerular apparatus fulfils several important regulatory functions in the kidney, such as tubuloglomerular feedback (TGF) control and control of renin release. The macula densa (MD) cells sense the fluid load by perceiving the distal NaCl concentration via a Na-K-2Cl cotransport system in the luminal cell membrane. It has been proposed that macula densa cell activation may involve changes in intracellular cytosolic free calcium concentration ([Ca2+]i), as one link in the chain of events activating TGF or releasing renin. We therefore investigated the changes in the intracellular calcium concentrations with fura-2, using a video system, in macula densa cells, and compared them with the changes in the corresponding concentrations in the ascending limb of the loop of Henle (c-TAL). The results show that our technique for analysing intracellular cytosolic free calcium in isolated perfused tubules is valid for this purpose, and the Kd value obtained was similar to that found by Grynkiewicz et al. (1985). The intracellular cytosolic free calcium concentration was about 90 nM both in the macula densa and c-TAL cells, and the macula densa cell intracellular cytosolic free calcium concentration increased by about 20 nM when the tubular lumen was perfused with Na and Cl at low concentrations. No significant changes were noted when furosemide was added to the perfusion solutions. We consider it hardly likely that this small change in intracellular cytosolic free calcium concentration can be entirely responsible for full activation of renin release or full inactivation of the TGF control mechanism. It would seem that the signal transmission from the macula densa cells could occur by other routes than through activation of intracellular cytosolic free calcium concentration.
球旁器在肾脏中发挥着多种重要的调节功能，如管球反馈（TGF）控制和肾素释放控制。致密斑（MD）细胞通过位于管腔细胞膜上的Na-K-2Cl共转运系统感知远端NaCl浓度，从而感知液体负荷。有人提出，致密斑细胞的激活可能涉及细胞内胞质游离钙浓度（[Ca2+]i）的变化，这是激活TGF或释放肾素的一系列事件中的一个环节。因此，我们使用视频系统，用fura-2研究了致密斑细胞内钙浓度的变化，并将其与髓袢升支粗段（c-TAL）中相应浓度的变化进行了比较。结果表明，我们用于分析分离灌注小管中细胞内胞质游离钙的技术适用于此目的，获得的Kd值与Grynkiewicz等人（1985年）发现的值相似。致密斑和c-TAL细胞中的细胞内胞质游离钙浓度均约为90 nM，当用低浓度的Na和Cl灌注管腔时，致密斑细胞内胞质游离钙浓度增加约20 nM。向灌注溶液中加入呋塞米后未观察到明显变化。我们认为，细胞内胞质游离钙浓度的这种小变化很难完全导致肾素释放的完全激活或TGF控制机制的完全失活。看来，致密斑细胞的信号传递可能通过细胞内胞质游离钙浓度激活以外的其他途径发生。
Zotero 插件