Nikpey Elham, Karlsen Tine V, Rakova Natalia, Titze Jens M, Tenstad Olav, Wiig Helge
From the Department of Biomedicine, University of Bergen, Norway (E.N., T.V.K., O.T., H.W.); Department of Medicine, Haukeland University Hospital, Bergen, Norway (E.N.); Experimental and Clinical Research Center, Charité Medical Facility and the Max-Delbrueck Center for Molecular Medicine, Berlin, Germany (N.R.); Junior Research Group 2, Interdisciplinary Center for Clinical Research, University Clinic Erlangen, Germany (J.M.T.); and Division of Clinical Pharmacology, Vanderbilt University Medical Center, Nashville, TN (J.M.T.).
Hypertension. 2017 Apr;69(4):660-668. doi: 10.1161/HYPERTENSIONAHA.116.08539. Epub 2017 Feb 6.
The common notion is that the body Na is maintained within narrow limits for fluid and blood pressure homeostasis. Several studies have, however, shown that considerable amounts of Na can be retained or removed from the body without commensurate water loss and that the skin can serve as a major salt reservoir. Our own data from rats have suggested that the skin is hypertonic compared with plasma on salt storage and that this also applies to skin interstitial fluid. Even small electrolyte gradients between plasma and interstitial fluid would represent strong edema-generating forces. Because the water accumulation has been shown to be modest, we decided to reexamine with alternative methods in rats whether interstitial fluid is hypertonic during salt accumulation induced by high-salt diet (8% NaCl and 1% saline to drink) or deoxycorticosterone pellet implantation. These treatments resulted both in increased systemic blood pressure, skin salt, and water accumulation and in skin hyperosmolality. Interstitial fluid isolated from implanted wicks and lymph draining the skin was, however, isosmotic, and Na concentration in fluid isolated by centrifugation and in lymph was not different from plasma. Interestingly, by eluting layers of the skin, we could show that there was an osmolality and urea gradient from epidermis to dermis. Collectively, our data suggest that fluid leaving the skin as lymph is isosmotic to plasma but also that the skin can differentially control its own electrolyte microenvironment by creating local gradients that may be functionally important.
通常的观念是，机体钠在很窄的范围内维持稳定，以保持体液和血压平衡。然而，多项研究表明，机体可以保留或排出大量的钠，而不会有相应的水分流失，并且皮肤可作为主要的盐储存库。我们自己对大鼠的研究数据表明，在储存盐分方面，皮肤相对于血浆是高渗的，这一点也适用于皮肤间质液。即使血浆和间质液之间存在很小的电解质梯度，也会产生强大的致水肿力。由于已证明水分积聚并不显著，我们决定用其他方法重新研究，在高盐饮食（饮用8%氯化钠和1%盐水）或植入脱氧皮质酮丸诱导大鼠盐分积聚期间，间质液是否为高渗状态。这些处理均导致全身血压升高、皮肤盐分和水分积聚以及皮肤高渗。然而，从植入的灯芯中分离出的间质液以及引流皮肤的淋巴液是等渗的，通过离心分离出的液体和淋巴液中的钠浓度与血浆无异。有趣的是，通过洗脱皮肤各层，我们可以发现从表皮到真皮存在渗透压和尿素梯度。总体而言，我们的数据表明，作为淋巴液离开皮肤的液体与血浆等渗，但皮肤也可以通过形成局部梯度来差异调节自身的电解质微环境，这可能具有重要的功能意义。
