Fluid, clearance

Fig. 3 Aquaporin deletion reduces osmotic water permeability in lung, but does not impair active fluid absorption, a AQP expression in epithelia and endothelia in nasopharyngeal cavity, upper and lower airways, and alveoli, b Osmotically driven water transport across the airspace/capillary barrier in perfused lungs from wildtype and indicated AQP null mice. Note the remarkable slowing of osmotic equilibration in mice lacking AQPl or AQP5. c Alveolar fluid clearance measured from the increased concentration of a volume marker 15 min after instillation of isosmolar fluid at 37°C. Where indicated, fluid absorption was inhibited by amiloride or stimulated by isoproterenol. From Bat et al. (1999) and Ma et al. (2000a)...

Durham RM, Moran JJ, Mazuski JE, Shapiro MJ, Baue AE, Flint LM (2003) Multiple organ failure in trauma patients. J Trauma 55(4) 608-616 Eckle T, Grenz A, Laucher S, Eltzschig HK (2008) A2B adenosine receptor signaling attenuates acute lung injury by enhancing alveolar fluid clearance in mice. J Clin Invest 118(10) 3301-3315... 

Impairs alveolar fluid clearance by inhibiting epithelial Na channels [178]... 

The rate of protein clearance has been estimated as 10% of the rate of fluid clearance from alveoli [173]. IgG clearance is probably mediated by FcRn transcytosis in distal type I alveolar epithelium and more proximal bronchial epithelium. Type I alveolar epithelium and bronchial epithelium contain the necessary subcellular structures for FcRn-mediated transcytosis vesicles, membrane invaginations, caveolae, and clathrin-coated pits [173,174], FcRn mRNA is expressed in lung although the cell types and locations have not yet been determined [112], Moreover, primary alveolar epithelial monolayer cell cultures express functional FcRn [173], plgA-R/SC transcytosis is thought to contribute little to distal (alveolar) airway IgG transport but might mediate more proximal (bronchial or bronchiolar) IgA transport [173], Uptake of an aerosolized IgG Fc-erythropoietin fusion molecule and subsequent erythropoietin-induced reticulocytosis has been demonstrated in human and nonhuman primates [175],... 

Rezaiguia, S., Garat, C., Delclaux, C., Meignan, M., Fleury, J., Legrand, P., Matthay, M. A., and Jayr, C. (1997) Acute bacterial pneumonia in rats increases alveolar epithelial fluid clearance by a tumor necrosis factor-alpha-dependent mechanism. J. Clin. Invest. 99,325-335. 

In mice, targeted transgenic expression of human Pj-adrenergic receptors to type II cells increased alveolar fluid clearance (McGraw et al. 2001). 

In anaesthetised male Sprague-Dawley rats subjected to 45 min of intestinal ischaemia followed by 3 h of reperfusion B5rjesson et al. (2000) found a 76 % increase in alveolar fluid clearance compared with the control values P <0.05). The stimulated alveolar liquid clearance seen after intestinal ischaemia-reperfusion was not inhibited by propranolol, indicating stimulation through a noncatecholamine-dependent pathway. Administration of a neutralising polyclonal anti-tumour necrosis-a antibody before induction of intestinal ischaemia completely inhibited the increased alveolar liquid clearance observed after intestinal ischaemia-reperfusion. 

Song, W., Wei, S., Zhou, Y, et al., 2010. Inhibition of lung fluid clearance and epithelial Na+ channels by chlorine, hypochlorous acid, and chloramines. J. Biol. Chem. 285, 9716-9728. 

Beneficial effects of growth factors such as KGF have been shown in some animal models of ALI, through the improvement of endothelial and epithelial barrier function, and enhanced rate of alveolar fluid clearance. Further animal studies and clinical trials are required to confirm this approach. The effect of KGF on pulmonary dysfunction in ALI patients is under investigation in a randomised placebo-controlled trial (KARE). This trial will assess the benefit of palifermin (recombinant KGF) in ALI patients. The use of growth factors against chemically induced lung injury may well be influenced by the outcome of such clinical trials in ALI patients. 

T. Sakuma, G. Okaniwa, T. Nakada, T. Nishimura, S. Fujimura and M. A. Matthay, Alveolar fluid clearance in the resected human lung, Am. J. Respir. Crit. Care Med., 1994,150, 305-310. 

Sakuma T, Hida M, Nambu Y, Osanai K, Toga H, Taka-hashi K, Ohya N, Inoue M, Watanahe Y. Betal-adrenergic agonist is a potent stimulator of alveolar fluid clearance in hyperoxic rat lungs. Japan. J. Pharmacol. 2001 85(2) 161-166. 

Ware LB, Matthay MA. Alveolar fluid clearance is impaired in the majority of patients with acute lung injiny and the acute respiratory distress syndrome. Am J Respir Crit Care Med 2001 163 1376-1383. 

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