Effects of SNP, ouabain, and amiloride on electrical potential profile of isolated sheep pleura

Factors Affecting Rate of Pleural Fluid Accumulation in Patients with Malignant Pleural Effusions

Purpose of Review

Malignant pleural effusions (MPEs) are initially treated with thoracocentesis but usually reaccumulate. There is wide variation in the rate of recurrence. Those with rapid recurrence could benefit from early definitive treatment, whilst those with slower recurrences may not. Here, we discuss pleural fluid homeostasis, MPE pathophysiology, and factors associated with reaccumulation.

Recent Findings

Few studies have investigated markers of MPE reaccumulation. Suggested features of rapid reaccumulation include lactate dehydrogenase, effusion size, positive cytology, and dyspnoea. Vascular endothelial growth factor (VEGF) correlates with MPE size and treatment response, but its association with reaccumulation rate is unknown. Some anti-VEGF therapies have shown promise in MPE management.

Summary

Further work is needed to validate hypothesised biomarkers of rapid recurrence and to characterise other biomarkers, such as VEGF. The Reaccumulation rate of Malignant Pleural Effusions After Therapeutic Aspiration (REPEAT) study aims to address these gaps in the literature and is currently in recruitment.

Aquaporin-1 Facilitates Transmesothelial Water Permeability: In Vitro and Ex Vivo Evidence and Possible Implications in Peritoneal Dialysis

We previously showed that mesothelial cells in human peritoneum express the water channel aquaporin 1 (AQP1) at the plasma membrane, suggesting that, although in a non-physiological context, it may facilitate osmotic water exchange during peritoneal dialysis (PD). According to the three-pore model that predicts the transport of water during PD, the endothelium of peritoneal capillaries is the major limiting barrier to water transport across peritoneum, assuming the functional role of the mesothelium, as a semipermeable barrier, to be negligible. We hypothesized that an intact mesothelial layer is poorly permeable to water unless AQP1 is expressed at the plasma membrane. To demonstrate that, we characterized an immortalized cell line of human mesothelium (HMC) and measured the osmotically-driven transmesothelial water flux in the absence or in the presence of AQP1. The presence of tight junctions between HMC was investigated by immunofluorescence. Bioelectrical parameters of HMC monolayers were studied by Ussing Chambers and transepithelial water transport was investigated by an electrophysiological approach based on measurements of TEA+ dilution in the apical bathing solution, through TEA+-sensitive microelectrodes. HMCs express Zo-1 and occludin at the tight junctions and a transepithelial vectorial Na+ transport. Real-time transmesothelial water flux, in response to an increase of osmolarity in the apical solution, indicated that, in the presence of AQP1, the rate of TEA+ dilution was up to four-fold higher than in its absence. Of note, we confirmed our data in isolated mouse mesentery patches, where we measured an AQP1-dependent transmesothelial osmotic water transport. These results suggest that the mesothelium may represent an additional selective barrier regulating water transport in PD through functional expression of the water channel AQP1.

Yellow Nail Syndrome or Diffuse Lymphatic Network Disease

We report a man aged 68 years old with pneumothorax and chronic bilateral pleural effusion in association with a history of yellow nails. The diagnosis of yellow nail syndrome based on yellow nails, lymphedema, chronic pleural effusion and intestinal lymphangiectasia.

Design considerations and challenges for mechanical stretch bioreactors in tissue engineering

With the increase in average life expectancy and growing aging population, lack of functional grafts for replacement surgeries has become a severe problem. Engineered tissues are a promising alternative to this problem because they can mimic the physiological function of the native tissues and be cultured on demand. Cyclic stretch is important for developing many engineered tissues such as hearts, heart valves, muscles, and bones. Thus a variety of stretch bioreactors and corresponding scaffolds have been designed and tested to study the underlying mechanism of tissue formation and to optimize the mechanical conditions applied to the engineered tissues. In this review, we look at various designs of stretch bioreactors and common scaffolds and offer insights for future improvements in tissue engineering applications. First, we summarize the requirements and common configuration of stretch bioreactors. Next, we present the features of different actuating and motion transforming systems and their applications. Since most bioreactors must measure detailed distributions of loads and deformations on engineered tissues, techniques with high accuracy, precision, and frequency have been developed. We also cover the key points in designing culture chambers, nutrition exchanging systems, and regimens used for specific tissues. Since scaffolds are essential for providing biophysical microenvironments for residing cells, we discuss materials and technologies used in fabricating scaffolds to mimic anisotropic native tissues, including decellularized tissues, hydrogels, biocompatible polymers, electrospinning, and 3D bioprinting techniques. Finally, we present the potential future directions for improving stretch bioreactors and scaffolds. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:543-553, 2016.

Can pharmacologic agents speed the rate of resorption of pleural fluid?

PURPOSE OF REVIEW

Pleural effusion is a common clinical problem resulting from a wide range of diseases. Treatment options include targeting the primary cause or, in persistent cases, invasive removal of the excess fluid from the pleural cavity. In this review, we summarize the experimental data concerning pharmacological agents that influence pleural fluid resorption and examine their potential as a novel noninvasive treatment strategy.

RECENT FINDINGS

Recently published evidence indicates that adrenergic agents and corticosteroids can increase pleural fluid clearance from the cavity. On the contrary, paracetamol and certain nonsteroid anti-inflammatory drugs can impede fluid outflow. These concepts are based on data extracted by in-vivo studies using provoked hydrothoraces in rabbits and mice, as well as by ex-vivo electrophysiological experiments using sheep and human pleural tissue.

SUMMARY

In conclusion, the available experimental data indicate that certain pharmacological agents may impact fluid resorption, thus affecting pleural fluid accumulation and the rate of pleural effusion resolution.

Tight junction physiology of pleural mesothelium

Pleura consists of visceral and parietal cell layers, producing a fluid, which is necessary for lubrication of the pleural space. Function of both mesothelial cell layers is necessary for the regulation of a constant pleural fluid volume and composition to facilitate lung movement during breathing. Recent studies have demonstrated that pleural mesothelial cells show a distinct expression pattern of tight junction proteins which are known to ubiquitously determine paracellular permeability. Most tight junction proteins provide a sealing function to epithelia, but some have been shown to have a paracellular channel function or ambiguous properties. Here we provide an in-depth review of the current knowledge concerning specific functional contribution of these proteins determining transport and barrier function of pleural mesothelium.

Role of histamine in altering fluid recycling in normal and post-traumatic rabbit peritoneum

This study aims to investigate if histamine induces electrochemical alterations in the normal and post-traumatic peritoneum. Peritoneal rabbit specimens were obtained before surgery and 10 days post-operatively and were mounted in Ussing chambers. Histamine solutions were added facing the intra-peritoneal and outer-peritoneal surface. Dimetindene maleate-, cetirizine-, and ranitidine-pretreated specimens were used to investigate histamine receptor involvement, whereas amiloride- and ouabain-pretreated specimens were used to investigate ion transportation blockage involvement. Trans-mesothelial resistance (R(TM)) was determined. Histamine-increased R(TM) intra-peritoneally and decreased it outer-peritoneally. A less intense effect was induced in post-traumatic specimens. Dimetindene maleate, cetirizine, amiloride, and ouabain totally inhibited this effect, whereas ranitidine only had a partial effect. Histamine induces electrochemical alterations in the normal and post-operative peritoneum. This effect is mediated by interaction with histamine receptors, hindering the normal process of ion trans-mesothelial transportation.

Endothelin-1 acutely reduces the permeability of visceral sheep peritoneum in vitro through both endothelin-A and endothelin-B receptors

Mesothelium is an important part of the peritoneal barrier for water and ion transport, essential for effective peritoneal dialysis (PD). Peritoneal fibrosis has been associated with PD treatment failure. Endothelin-1 (ET-1) is a potent vasoactive peptide, involved in pathologic fibrotic processes. Its action is mediated mainly by endothelin type A (ETA ) and type B (ETB ) receptors. The aim of this study was to investigate, by Ussing chamber experiments, the effect of ET-1 on the transmesothelial electrical resistance (RTM ) of the isolated visceral sheep peritoneum. Intact sheets of visceral peritoneum were obtained from 40 adult sheep and mounted in Ussing-type chambers. ET-1 (10(-7)  M), BQ-123 (ETA receptor antagonist; 10(-6)  M), BQ-788 (ETB receptor antagonist; 10(-6)  M), and their combinations were added on the apical and the basolateral side of the peritoneum. RTM was measured before and serially after addition of the substances, and changes were registered as percentage (ΔRTM %). RTM increased within 1 min after addition of ET-1 apically (ΔRTM 65.03 ± 15.87%; P < 0.05) or basolaterally (ΔRTM 85.5 ± 20.86%; P < 0.05). BQ-123 and BQ-788 and their combination significantly reduced (P < 0.05) the effect of ET-1 to a similar degree in all cases. These results clearly indicate that ET-1 reduces ionic permeability of the visceral sheep peritoneum in vitro. Additionally, it is obvious that this inhibitory effect is mediated through both ETA and ETB receptors.

IGF-1 alters the human parietal pleural electrochemical profile by inhibiting ion trans-cellular transportation after interaction with its receptor

OBJECTIVE

The effect of IGF-1 in the human pleural permeability and the underlying mechanisms involved were investigated.

DESIGN

Specimens from thoracic surgical patients were mounted in Ussing chambers. Solutions containing IGF-1 (1 nM-100 nM) and IGF-1 Receptor Inhibitor (1 μΜ), amiloride 10 μM (Na(+) channel blocker) and ouabain 1 mM (Na(+)-K(+) pump inhibitor) were used in order to investigate receptor and ion transporter involvement respectively. Trans-mesothelial Resistance (R(TM)) across the pleural membrane was determined as a permeability indicator. Immunohistochemistry for IGF-1 receptors was performed.

RESULTS

IGF-1 increased R(TM) when added on the interstitial surface for all concentrations (p=.008, 1 nM-100 nM) and decreased it on the mesothelial surface for higher concentrations (p=.046, 100 nM). Amiloride and ouabain inhibited this effect. The IGF-1 Receptor Inhibitor also totally inhibited this effect. Immonuhistochemistry demonstrated the presence of IGF-1 receptors in the pleura.

CONCLUSIONS

It is concluded that IGF-1 changes the electrophysiology of the human parietal pleura by hindering the normal ion transportation and therefore the pleural fluid recycling process. This event is achieved after IGF-1 interaction with its receptor which is present in the human pleura.

Variation of the postoperative fluid drainage according to the type of lobectomy

OBJECTIVES

The pleural membrane of the lower pleural cavity has a greater ability to recycle fluid than the pleural membrane of the upper pleural cavity. During lobectomy, the visceral pleura is removed with the lobe, whereas the parietal pleura is traumatized during manipulation. This study investigates variations of the drainage according to the type of lobectomy and its relation to effusion-related complications.

METHODS

Data of upper and lower lobectomy patients were compared with those of wedge resection patients. All patients were suctioned until totally dry before closure, and one chest tube was left in the hemithorax. The amount of fluid drained per day, the duration of drainage, the length of hospital stay and the morbidity were noted. Student's paired t-test and Mann-Whitney U-test were used for comparison; P < 0.05 was defined as statistically significant.

RESULTS

Patients after lower lobectomy had more fluid drained when compared with patients after upper lobectomy or wedge resection on the first (636 ± 90, 268 ± 75 and 225 ± 62 ml, respectively; P = 0.002) and second postoperative day (464 ± 94, 237 ± 90 and 220 ± 62 ml, respectively; P = 0.046). The drainage tube was removed earlier in patients with upper lobectomy procedures than in patients with lower lobectomy procedures (4.6 ± 0.9 vs 8.1 ± 1.4 days; P = 0.014). Effusion-related complications developed in lower lobectomies with a higher output from the second postoperative day.

CONCLUSIONS

A larger amount of fluid is drained after removal of the lower lobes, possibly because the important fluid-recycling ability of the lower parts of the cavity is malfunctioning. Early drainage tube removal after lower lobectomy may be reconsidered when taking into account the possibility of effusion-related complications.

Permeability of the arachnoid and pia mater. The role of ion channels in the leptomeningeal physiology

PURPOSE

The purpose of this paper is to study the ionic permeability of the leptomeninges related to the effect of ouabain (sodium-potassium-ATPase inhibitor) and amiloride (epithelial sodium channel (ENaC) inhibitor) on the tissue, as well as identify the presence of ion channels.

METHODS

Cranial leptomeningeal samples from 26 adult sheep were isolated. Electrophysiological measurements were performed with Ussing system and transmembrane resistance values (R(TM) in Ω*cm(2)) obtained over time. Experiments were conducted with the application of ouabain 10(-3) M or amiloride 10(-5) M at the arachnoidal and pial sides. Immunohistochemical studies of leptomeningeal tissue were prepared with alpha-1 sodium-potassium-ATPase (ATP1A1), beta-ENaC, and delta-ENaC subunit antibodies.

RESULTS

The application of ouabain at the arachnoidal side raised the transmembrane resistance statistically significantly and thus decreased its ionic permeability. The addition of ouabain at the pial side led also to a significant but less profound increment in transmembrane resistance. The addition of amiloride at the arachnoidal or pial side did not produce any statistical significant change in the R(TM) from controls (p > 0.05). Immunohistochemistry confirmed the presence of the ATP1A1 and beta- and delta-ENaC subunits at the leptomeninges.

CONCLUSIONS

In summary, leptomeningeal tissue possesses sodium-potassium-ATPase and ENaC ion channels. The application of ouabain alters the ionic permeability of the leptomeninges thus reflecting the role of sodium-potassium-ATPase. Amiloride application did not alter the ionic permeability of leptomeninges possibly due to localization of ENaC channels towards the subarachnoid space, away from the experimental application sites. The above properties of the tissue could potentially be related to cerebrospinal fluid turnover at this interface.

Effect of histamine on the electrophysiology of the human parietal pleura

INTRODUCTION

Histamine is involved in the pathogenesis of numerous diseases and regulates the permeability of different tissues. The aim of this study is to investigate the effects of histamine on the electrophysiology of human parietal pleura and the underlying mechanisms involved.

MATERIALS AND METHODS

Pleural specimens were obtained from patients subjected to thoracic surgery and were mounted in Ussing chambers. Histamine solutions (1μM to 1mM) were applied in native and pretreated specimens with dimetindene maleate, cetirizine, ranitidine, amiloride and ouabain. Trans-mesothelial resistance was determined (R(TM)).

RESULTS

Histamine induced a rapid R(TM) increase on the mesothelial (p = 0.008) and a decrease on the interstitial surface (p = 0.029). This effect was dose-dependent and was totally abolished by dimetindene maleate, cetirizine and amiloride and partially by ranitidine and ouabain.

CONCLUSIONS

Histamine induces acute electrochemical changes in human pleura mainly via interaction with the H(1) and partially with the H(2) histamine receptors. It also interferes with trans-cellular permeability and therefore may participate in pleural fluid recycling.

Tight junction proteins contribute to barrier properties in human pleura

The permeability of pleural mesothelium helps to control the volume and composition of the liquid lubricating pleural surfaces. Information on pleural barrier function in health and disease, however, is scarce. Tissue specimens of human pleura were mounted in Ussing chambers for measurement of transmesothelial resistance. Expression of tight junction (TJ) proteins was studied by Western blots and immune fluorescence confocal microscopy. Both visceral and parietal pleura showed barrier properties represented by transmesothelial resistance. Occludin, claudin-1, -3, -5, and -7, were detected in visceral pleura. In parietal pleura, the same TJ proteins were detected, except claudin-7. In tissues from patients with pleural inflammation these tightening claudins were decreased and in visceral pleura claudin-2, a paracellular channel former, became apparent. We report that barrier function in human pleura coincides with expression of claudins known to be key determinants of epithelial barrier properties. In inflamed tissue, claudin expression indicates a reduced barrier function.

Insulin-induced electrophysiology changes in human pleura are mediated via its receptor

Background. Insulin directly changes the sheep pleural electrophysiology. The aim of this study was to investigate whether insulin induces similar effects in human pleura, to clarify insulin receptor's involvement, and to demonstrate if glibenclamide (hypoglycemic agent) reverses this effect. Methods. Human parietal pleural specimens were mounted in Ussing chambers. Solutions containing insulin or glibenclamide and insulin with anti-insulin antibody, anti-insulin receptor antibody, and glibenclamide were used. The transmesothelial resistance (R_TM) was determined. Immunohistochemistry for the presence of Insulin Receptors (IRa, IRb) was also performed. Results. Insulin increased R_TM within 1st min (P = .016), when added mesothelially which was inhibited by the anti-insulin and anti-insulin receptor antibodies. Glibenclamide also eliminated the insulin-induced changes. Immunohistochemistry verified the presence of IRa and IRb. Conclusion. Insulin induces electrochemical changes in humans as in sheep via interaction with its receptor. This effect is abolished by glibenclamide.

Dexamethasone decreases the transmesothelial electrical resistance of the parietal and visceral pleura

The effect of dexamethasone on the transmesothelial electrical resistance (R(TM)) of sheep pleura was investigated by Ussing chamber experiments. Our results show that dexamethasone decreases the R(TM) of sheep pleurae, in part by stimulation of glucocorticoid receptors. This finding may be of importance in regard to the faster resolution of corticosteroid-treated pleural effusions.

Pleural electrophysiology variations according to location in pleural cavity

The aim of the study was to compare the electrophysiology profile of sheep pleura originated from different locations of the pleural cavity with the respective profile in humans. Sheep specimens obtained from upper and lower lung lobes, 1st-4th and 8th-12th rib, ventral-dorsal diaphragm and mediastinum were mounted between Ussing chambers. Human visceral tissues were obtained from patients subjected to lobectomy. Trans-mesothelial resistance (R(TM)) was determined as an indicator of the tissue permeability, while amiloride and ouabain were used as inhibitors of cellular transportation via ion transporters. Control values R(TM) were low in lower lobe visceral, caudal costal parietal and diaphragmatic pleura. Amiloride increased R(TM) at all locations except upper visceral and mediastinum. Higher R(TM) increases were found in caudal parietal and dorsal diaphragmatic samples. Ouabain increased R(TM) of lower visceral, caudal parietal and diaphragmatic pleura but not of mediastinal specimens. Observations made in sheep tissue were comparable with human visceral, parietal and mediastinal regions. In conclusion, results suggest heterogeneity of trans-mesothelial permeability among different pleural locations in sheep as was the case for humans. Thoracic surgeons should consider physiology function of each part of pleural cavity before pleural tissue manipulation. Observations made in sheep may be used to understand human physiology.

Electrolyte and Fluid Transport in Mesothelial Cells

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.

Pleural liquid and its exchanges

After an account on morphological features of visceral and parietal pleura, mechanical coupling between lung and chest wall is outlined. Volume of pleural liquid is considered along with its thickness in various regions, and its composition. Pleural liquid pressure (P(liq)) and pressure exerted by lung recoil in various species and postures are then compared, and the vertical gradient of P(liq) considered. Implications of lower P(liq) in the lung zone than in the costo-phrenic sinus at iso-height are pointed out. Mesothelial permeability to H(2)O, Cl(-), Na(+), mannitol, sucrose, inulin, albumin, and various size dextrans is provided, along with paracellular "pore" radius of mesothelium. Pleural liquid is produced by filtration from parietal pleura capillaries according to Starling forces. It is removed by absorption in visceral pleura capillaries according to Starling forces (at least in some species), lymphatic drainage through stomata of parietal mesothelium (essential to remove cells, particles, and large macromolecules), solute-coupled liquid absorption, and transcytosis through mesothelium.

Amiloride-sensitive sodium channels on the parietal human peritoneum: evidence by ussing-type chamber experiments

The mesothelium is part of the peritoneal water and ion transport barrier essential for peritoneal dialysis (PD) treatment and has a central role in the pathogenesis of peritoneal fibrosis and ultrafiltration failure observed in many PD patients. We investigated the effect of amiloride on the transmesothelial electrical resistance (RTM) of isolated parietal human peritoneum. Intact sheets were obtained from seven patients (three men, four women; mean age, 64 +/- 8 years). Fourteen peritoneal planar sheets were transferred to the laboratory in oxygenated Krebs-Ringer bicarbonate solution at 4 degrees C within 30 minutes after removal and mounted in an Ussing-type chamber. Amiloride (10(-3) mol/L) added apically (n = 8) caused a rapid rise of the RTM to 24.15 +/- 0.76 [OMEGA]H cm2 and a subsequent value persistence (p < 0.05); added basolaterally (n = 6), it increased the RTM to 22.66 +/- 0.59 [OMEGA]H cm2 within 1 minute, which persisted throughout the experiment. RTM was measured before and serially for 30 minutes after addition of amiloride. Control RTM was 20.29 +/- 0.86 [OMEGA]H cm2. These results indicate a rapid inhibitory effect of amiloride on the ionic permeability of parietal human peritoneum. The increase in the RTM observed after addition of amiloride clearly indicates the existence of amiloride-sensitive sodium channels on the human parietal peritoneal membrane, which may play some role in the ultrafiltration process and sodium removal during PD.

Comparison of the electrophysiological properties of the sheep isolated costal and diaphragmatic parietal pleura

1. Pleural permeability may contribute to pleural fluid turnover. The transmesothelial resistance (R(TM)), is an established surrogate of mesothelial permeability. The aim of the present study was to compare the electrophysiological properties of costal and diaphragmatic parietal pleura. 2. Specimens of the parietal pleura were isolated from 12 adult sheep from the chest wall and the diaphragm. Electrophysiological measurements were conducted with the Ussing system. Specimens of the parietal pleura of both types (diaphragmatic and costal) were compared histologically and total protein content measurements were also made. 3. The R(TM) of the diaphragmatic parietal pleura was significantly higher than that of the costal parietal pleura throughout the experiment. The diaphragmatic parietal pleura contains more cuboidal cells than the costal parietal pleura and its protein content was higher, however this difference was not statistically significant. 4. The costal parietal pleura consists of a more 'leaky' mesothelium than the diaphragmatic pleura. The morphological differences between the two types of parietal pleura may underline the electrophysiological findings.

Transport properties of the mesothelium and interstitium measured in rabbit pericardium

The contribution of the pleural mesothelium to pleural liquid and protein transport is still vigorously debated. Recent in vitro studies of stripped pleural membrane and free-standing pericardium have demonstrated active ion solute coupled transport of liquid and transcytosis of protein. However, the relative contribution of the passive transport properties of the pleural mesothelium compared to the pleural interstitium has not been extensively studied. In in vitro studies, we measured the albumin diffusion coefficient, reflection coefficient, hydraulic conductivity and electrical resistance of rabbit pericardium. We used two techniques, treatment with 40 muM nocodazole and a 1-min hypotonic cell lysis with distilled water, to eliminate the effect of the two mesothelial layers on diffusional and hydraulic resistances. Each technique increased the albumin diffusion coefficient and hydraulic conductivity 3- to 4-fold. In hydraulic conductivity experiments using tracer 125I-albumin, nocodazole reduced the reflection coefficient to zero, rendering the pericardium completely permeable to albumin. We applied the cell-lysis technique to the pleural and pericardial mesothelium in sequence to evaluate the separate contribution of each mesothelium. Both diffusional and hydraulic resistances, but not electrical resistance, of the mesothelium were overestimated by the cell-lysis technique. The pleural mesothelium contributed at most 30% of diffusional resistance, 10% of hydraulic resistance and 14% of electrical resistance of the total pericardial resistances. We conclude that the pleural mesothelium is not the primary barrier to protein diffusion or bulk flow of liquid from the pericardial microcirculation to the pleural liquid.

Effect of adrenaline on transmesothelial resistance of isolated sheep pleura

The effect of adrenaline on the transmesothelial resistance (RTM) of sheep's visceral and parietal pleura was studied using the Ussing chamber technique. Basal transmesothelial resistance of visceral pleura was found to be 20.71 +/- 0.31 Omega cm2, whereas that of parietal pleura was found to be 19.53 +/- 0.34 Omega cm2. Immediately after the addition of adrenaline (10(-7) M) both apically and basolaterally on the visceral and parietal pleura, these values were significantly increased (P < 0.05). Addition of the nonselective beta-receptor blocker, propranolol (10(-5) M), suppressed this effect in both visceral and parietal pleura, while addition of the nonselective alpha-receptor blocker, phentolamine (10(-5) M), partly suppressed the above-mentioned increase in the parietal pleura. In conclusion, our results show that adrenaline has a rapid effect on both pleurae. This rapid effect is mediated by the stimulation of beta-adrenergic receptors in the case of visceral pleura, while in the case of parietal pleura this effect seems to be due to a stimulation of alpha- and beta-adrenergic receptors. On the visceral pleura the effect of adrenaline vanishes after some minutes and on the parietal this effect is more permanent than the visceral's one, suggesting differences in the distribution of the adrenergic receptors between the visceral and parietal pleura.

mu-Opioid influence on transmesothelial resistance of isolated sheep pleura and parietal pericardium

The effect of morphine (mu-opioid receptor agonist) on the transmesothelial resistance (R(TM)) of sheep's pleura and parietal pericardium was studied using the Ussing chamber technique. Basal transmesothelial resistance of parietal pleura was found to be 19.57+/-0.32 Omega cm2 and of visceral pleura was found to be 19.41+/-0.31 Omega cm2, whereas that of parietal pericardium was found to be 22.83+/-0.4 Omega cm2. Immediately after the addition of morphine (10(-9) M) both apically and basolaterally on the parietal pleura and parietal pericardium, these values were significantly increased (P<0.05). On the contrary, addition of morphine (10(-9) M) resulted in a rapid increase, only when placed basolaterally on the visceral pleura (P<0.05). In conclusion, our findings suggest that morphine, probably through mu-opioid stimulation, increases in vitro the transmesothelial resistance of the parietal pleura, of the visceral pleura when added basolaterally and of the parietal pericardium.

Enhancement of the Transmesothelial Resistance of the Parietal Sheep Peritoneum by Epinephrine In Vitro: Ussing-type Chamber Experiments

The peritoneal mesothelium constitutes an ion transport barrier that is taken advantage of in peritoneal dialysis. The aim of this study was to investigate the effects of epinephrine on the electrical transmesothelial resistance (R(TM)) of the isolated parietal sheep peritoneum by means of Ussing-type chamber experiments. Intact parietal (diaphragmatic) peritoneal samples were obtained from adult sheep immediately after sacrifice and transferred within 0.5 h to the laboratory in a cooled Krebs-Ringer bicarbonate solution (4 degrees C, pH 7.5), bubbled with 95% O2-5% CO2. A parietal peritoneal planar sheet was mounted in a Ussing-type chamber. Epinephrine (10(-7) M) was added to the apical and the basolateral side. The R(TM) was measured before and serially after the addition of epinephrine for 30 min. As active ion transport is temperature-dependent, all measurements were performed at 37 degrees C. The results were calculated as means with standard errors (x +/- SE) of six independent experiments. The control R(TM) was 20.05 +/- 0.61 ohm x cm2. The addition of epinephrine to the basolateral side within 1 min induced an increase of R(TM) to 21.8 +/- 0.45 ohm x cm2, which decreased thereafter progressively to reach control values again after 15 min. A similar effect of epinephrine on the apical side was apparent with a rapid rise of R(TM) to 22.5 +/- 0.66 ohm x cm2 and a subsequent decrease (P < 0.05). A clear association between the R(TM) and active ion transport was established from previous studies. The results of our study indicate a rapid action of epinephrine on the parietal peritoneum permeability.

Functional similarities between pleura and the renal proximal tubule – membrane and cellular considerations

The small amount of liquid that, under physiological conditions, is presented in the pleural cavity has been the focus of extensive research for more than a century. However, there are still unanswered questions and considerable controversies about the nature of the forces governing its movement into and out of the pleural cavity. Early in the 20th century has been proposed that pleural fluid turnover is simple based on the balance between hydraulic and colloid osmotic pressures existing across the pleural membranes. This original hypothesis has not been validated by data accumulating over the last 20 years. Pleural tissues and renal proximal tubules present high water permeability, small transepithelial electrical resistance (22.02 Omega cm2) and the same cation transportation such as Na+ channels, Na+-K+ ATPase channels, and Na+-H+ exchanger. In contrast to previous conflicting theories concerning pleura fluid movement, the same functional characteristics suggest the hypothesis that physiology of pleura is similar to proximal tubules.

Pleural mechanics and fluid exchange

The pleural space separating the lung and chest wall of mammals contains a small amount of liquid that lubricates the pleural surfaces during breathing. Recent studies have pointed to a conceptual understanding of the pleural space that is different from the one advocated some 30 years ago in this journal. The fundamental concept is that pleural surface pressure, the result of the opposing recoils of the lung and chest wall, is the major determinant of the pressure in the pleural liquid. Pleural liquid is not in hydrostatic equilibrium because the vertical gradient in pleural liquid pressure, determined by the vertical gradient in pleural surface pressure, does not equal the hydrostatic gradient. As a result, a viscous flow of pleural liquid occurs in the pleural space. Ventilatory and cardiogenic motions serve to redistribute pleural liquid and minimize contact between the pleural surfaces. Pleural liquid is a microvascular filtrate from parietal pleural capillaries in the chest wall. Homeostasis in pleural liquid volume is achieved by an adjustment of the pleural liquid thickness to the filtration rate that is matched by an outflow via lymphatic stomata.

Effect of amiloride in human and sheep parietal pleura

The fluid and solute transport properties of human parietal pleura were studied and compared with sheep parietal pleura in vitro. The pleura was mounted as a planar sheet between Ussing-type chambers. The results presented are the mean values of nine different experiments. The transepithelial electrical resistance (R(TE)) of both pleurae species was measured before and after the addition of amiloride in both sides of pleura. The R(TE) for human was 25.74 +/- 1.23 Ohm x cm(2), while for the sheep it was 38.18 +/- 0.83 Ohm x cm(2). The addition of amiloride to the serosal bathing solution increased the R(TE) of human pleura to 30.48 +/- 1.01 Ohm x cm(2) and sheep pleura to 40.32 +/- 0.82 Ohm x cm(2), while amiloride had no effect on the basolateral side. From the above, it is strongly suggested that the human pleura seems to be more leaky than sheep pleura. Although the R(TE) was increased in both pleurae, the elevation in human pleura was significantly higher, thus results from experiments in sheep pleura could only partly be extrapolated in human pleura.

Rapid effects of 17beta-estradiol and progesterone on sheep visceral and parietal pleurae via a nitric oxide pathway

We investigated the effects of 17beta-estradiol and progesterone on transepithelial electrical resistance (R(TE)) in sheep visceral and parietal pleurae. Specimens of intact pleurae from adult female sheep were used. The samples were transferred to the laboratory within 30 min after death of the animal in a Krebs-Ringer solution at 4 degrees C. The pleura was then mounted as a planar sheet in Ussing-type chambers, and electrical measurements were made. There was an increase in R(TE) in all of the samples examined after addition of 17beta-estradiol and progesterone in visceral and parietal pleurae. This increase was rapid within 1 min, lasted for ~15 min, returned to the basal level within 30-45 min, and was dose dependent. Tamoxifen, an estrogen receptor antagonist, did not significantly eliminate the effect of 17beta-estradiol. Furthermore, no steroid receptors were identified in cytosolic preparations of visceral and parietal pleura with ligand binding assays. The estrogen- and progesterone-induced increase in R(TE) in both visceral and parietal pleurae was affected by addition of an inhibitor of nitric oxide synthase. Indeed, previous administration of N(omega)-nitro-L-arginine methyl ester prevented the increase in R(TE) by 17beta-estradiol and progesterone. These results suggest that 17beta-estradiol and progesterone induce an increase in R(TE) in both visceral and parietal pleura and thus alter the transepithelial permeability. The effect of steroids may be accounted for by rapid release of nitric oxide in pleura.