Protein egress and entry rates in pleural fluid and plasma in sheep

Wiener-Kronish, J. P.; Albertine, Kurt H.; Ličko, Vojtech; Staub, Norman C.

doi:10.1152/jappl.1984.56.2.459

Cited by 46 publications

(29 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…For example, the volume of pleural fluid results from a balance of fluid inflow and outflow, occurring by Starling forces (assuming filtration through the parietal, and absorption through the visceral mesothelium), amiloride-sensitive lymphatic drainage through the parietal pleura stomas, and electrolyte-coupled fluid absorption through the mesothelium of both sides [55,56]. In humans, the balanced rate of fluid secretion and absorption in the steady state is ~0.01 ml kg −1 h −1 [57]. Compelling evidence, as reviewed in this manuscript, confirms the critical role played by mesothelial cells in fluid transport across the serosal cavities.…”

Section: Physiological and Clinical Relevancementioning

confidence: 99%

Electrolyte and Fluid Transport in Mesothelial Cells

Ji¹,

Nie²

2008

JEBP

View full text Add to dashboard Cite

Mesothelial cells are specialized epithelial cells, which line the pleural, pericardial, and peritoneal cavities. Accumulating evidence suggests that the monolayer of mesothelial cells is permeable to electrolyte and fluid, and thereby govern both fluid secretion and re-absorption in the serosal cavities. Disorders in these salt and fluid transport systems may be fundamental in the pathogenesis of pleural effusion, pericardial effusion, and ascites. In this review, we discuss the location, physiological function, and regulation of active transport (Na + -K + -ATPase) systems, cation and anion channels (Na + , K + , Cl − , and Ca 2+ channels), antiport (exchangers) systems, and symport (co-transporters) systems, and water channels (aquaporins). These secretive and absorptive pathways across mesothelial monolayer cells for electrolytes and fluid may provide pivotal therapeutical targets for novel clinical intervention in edematous diseases of serous cavities. Keywords mesothelioma; ion channel; permeability; effusion; filtration; ENaC Mesothelial cells are specialized epithelial cells that line the serous cavities, including the pleural, pericardial, and peritoneal cavities in addition to internal organs [1]. While the mesothelium was first described more than a century ago, one of its critical essential functions, namely, its active roles in transerosal transport, in particular, cavity fluid secretion and reabsorption, was long overlooked. Only in last two decades compelling evidence accumulated that mesothelial cells actively transport electrolytes and fluid and, in turn, regulate liquid volume within the cavities. The mesothelium, on the basis of recent increasing experimental evidence, both in vitro and in vivo, is less permeable to electrolytes than was previously assumed, with ion permeability characteristics similar to those in epithelia [2,3]. Herein this article we will review the expression and biophysical features of salt and fluid transport systems, both active and passive, that have been identified in mesothelial cells (Fig. 1, Tables 1 and 2). I. ION CHANNELS AND ATPASE I-1. Amiloride-Inhibitable Cation ChannelsThe epithelial sodium channel (ENaC), as a major pathway which participates in sodium movement across the apical membrane of polarized epithelial cells, has been cloned and characterized [4][5][6] ENaC subunits have been cloned to date, namely α-, β-, γ-, δ-, and ε-ENaC [7]. The biophysical properties of various ENaC channels depend on their subunit compositions. When expressed in oocytes one of "conductive" subunits (α, δ, and ε-ENaC) can form a channel sharing identical biophysical properties to three-subunit channels composed of both a "conductive" subunit and two "non-conductive" subunits, namely, β-and γ-ENaCs. When α-, β-, and γ-ENaC subunits are assembled together, the result is a 4-to 6-pS channel that is highly selective for Na + over K + . In contrast, two-subunit α β-and α γ-ENaC channels display diverse amiloride sensitivity, conductance, and Na + permeability [8]. ENaC is...

show abstract

Section: Physiological and Clinical Relevancementioning

confidence: 99%

Electrolyte and Fluid Transport in Mesothelial Cells

Ji¹,

Nie²

2008

JEBP

View full text Add to dashboard Cite

show abstract

“…This includes the liquid that cannot be collected, because it adheres to the walls of the space (0.30) (0.52 mL in rabbits [13,57], and 1.80 mL in dogs [13]), and the liquid that can be collected (0.13-0.20 mL?kg -1 in rabbits [8,13,57,58], and 0.06-0.10 mL?kg -1 in dogs [13,59]. In sheep, 0.08 mL?kg -1 can be collected [60,61]. When related to a measure of surface area (body weight to the 2/3 power), this volume ranges 0.13-0.27 mL?kg -2/3 .…”

Section: Pleural Liquidmentioning

confidence: 99%

Physiology and pathophysiology of pleural fluid turnover

Zocchi¹

2002

Eur Respir J

170

View full text Add to dashboard Cite

Tight control of the volume and composition of the pleural liquid is necessary to ensure an efficient mechanical coupling between lung and chest wall. Liquid enters the pleural space through the parietal pleura down a net filtering pressure gradient. Liquid removal is provided by an absorptive pressure gradient through the visceral pleura, by lymphatic drainage through the stomas of the parietal pleura, and by cellular mechanisms. Indeed, contrary to what was believed in the past, pleural mesothelial cells are metabolically active, and possess the cellular features for active transport of solutes, including vesicular transport of protein. Furthermore, the mesothelium was shown, on the basis of recent experimental evidence, both in vivo and in vitro, to be a less permeable barrier than previously believed, being provided with permeability characteristics similar to those of the microvascular endothelium. Direct assessment of the relative contribution of the different mechanisms of pleural fluid removal is difficult, due to the difficulty in measuring the relevant parameters in the appropriate areas, and to the fragility of the mesothelium. The role of the visceral pleura in pleural fluid removal under physiological conditions is supported by a number of findings and considerations.Further evidence indicates that direct lymphatic drainage through the stomas of the parietal pleura is crucial in removing particles and cells, and important in removing protein from the pleural space, but should not be the main effector of fluid removal. Its importance, however, increases markedly in the presence of increased intrapleural liquid loads. Removal of protein and liquid by transcytosis, although likely on the basis of morphological findings and suggested by recent indirect experimental evidence, still needs to be directly proven to occur in the pleura. When pleural liquid volume increases, an imbalance occurs in the forces involved in turnover, which favours fluid removal. In case of a primary abnormality of one ore more of the mechanisms of pleural liquid turnover, a pleural effusion ensues. The factors responsible for pleural effusion may be subdivided into three main categories: those changing transpleural pressure balance, those impairing lymphatic drainage, and those producing increases in mesothelial and capillary endothelial permeability. Except in the first case, pleural fluid protein concentration increases above normal: this feature underlies the classification of pleural effusions into transudative and exudative. Eur Respir J 2002; 20: 1545-1558. The thin layer of liquid present between the pleural surfaces has the important function of providing the mechanical coupling between the chest wall and lung, which ensures instantaneous transmission of perpendicular forces between the two structures, and allows their sliding in response to shearing forces [1,2]. It also provides lubrication of the reciprocal motions of the two structures during breathing. Two views, in part compatible, exist on the nature of t...

show abstract

“…It is important to recall that, in order to derive indications on pleural fluid turnover, one must carry out experiments in conditions close to the physiological one that is characterized by two main features: namely, a small pleural liquid volume and subatmospheric pleural liquid pressures, such as those occurring during spontaneous breathing. In experimental models implying large pleural effusions and mechanical ventilation [24,25], the database is difficult to interpret as it does not reflect a steady state situation.…”

Section: Pleural Fluid Filtrationmentioning

confidence: 99%

“…Although figures will vary in man, the overall situation is unlikely to be qualitatively different based on anotomofunctional considerations. data on pleural lymph flow were gathered in sheep, where the same group of investigators found on different occasions that pleural lymphatics would drain either <1% [25] or ≈70% of pleural fluid [24].…”

Section: Pleural Fluid Drainagementioning

confidence: 99%

Physiology and pathophysiology of pleural fluid turnover

Miserocchi¹

1997

Eur Respir J

240

126

View full text Add to dashboard Cite

Number 1 in this SeriesA review on pleural space is certainly most welcome, for the simple reason that on opening a textbook of physiology the concepts concerning pleural fluid turnover date back to 1927 [1]. The same comment, in fact, applies in general to microvascular water and solute exchange. This appears particularly misleading, considering the major advances achieved in the field over the last 70 yrs. Around the turn of the 19th century, STARLING and TUBBY [2] interpreted microvascular fluid and solute exchange as resulting from the balance between hydraulic and colloidosmotic pressures. This concept is still valid today, but the complete formulation of transmicrovascular exchange has become much more complex because water crosses biological membranes more easily than large solutes (namely, plasma proteins) do [3]. In fact, different equations describe water and solute fluxes [4].As a result, the general model of transcapillary fluid exchange still taught to students, based on fluid filtration at the arteriolar end of the capillary bed and reabsorption at the venular end, appears rather simplistic. Due to the different permeability to water and solutes, one could predict on a mathematical basis that such a model would lead to a progressive increase in interstitial protein concentration over time [3,4], a condition that cannot be confirmed experimentally.Similarly, the old hypothesis claiming that pleural fluid filters at parietal level and is reabsorbed through the visceral pleura [1] would imply that pleural liquid protein concentration would keep increasing with age, but again there are no indications that this occurs. The existence of partial restriction to the movement of large solutes, compared to that of water molecules, posed scientists the major problem of explaining how interstitial volume and protein concentration are kept fairly steady. Ideologically, this led to re-evaluation of lymphatics as the major route for interstitial fluid drainage. In fact, since lymphatics do not sieve proteins, they leave the interstitial protein concentration unaltered the latter depending only upon the sieving properties of the filtering membrane. Accordingly, the description of interstitial fluid homeostasis under steady state conditions is now being explained as a balance between capillary filtration and lymphatic absorption. Major validation of this model has come from the accumulating experimental data over the past 30 yrs concerning interstitial tissues [4] and serous spaces [5]. Interestingly, since the pioneering, work of STARLING and TUBBY [2] the pleural space has been used as a useful experimental model to study the interaction between microvascular filtration and lymphatic drainage.This article presents an integrated view of pleural fluid turnover, based on data gathered from experimental studies on animals over the last 15 yrs. The situation in man is, unfortunately, still poorly defined; yet, where possible, Under physiological conditions, the lung interstitium and the pleural space behave as function...

show abstract

Protein egress and entry rates in pleural fluid and plasma in sheep

Cited by 46 publications

References 0 publications

Electrolyte and Fluid Transport in Mesothelial Cells

Electrolyte and Fluid Transport in Mesothelial Cells

Physiology and pathophysiology of pleural fluid turnover

Physiology and pathophysiology of pleural fluid turnover

Contact Info

Product

Resources

About