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PubMed2007

Assessing pulmonary permeability by transpulmonary thermodilution allows differentiation of hydrostatic pulmonary edema from ALI/ARDS.

OBJECTIVE: To test whether assessing pulmonary permeability by transpulmonary thermodilution enables to differentiate increased permeability pulmonary edema (ALI/ARDS) from hydrostatic pulmonary edema. DESIGN: Retrospective review of cases. SETTING: A 24-bed medical intensive care unit of a university hospital. PATIENTS: Forty-eight critically ill patients ventilated for acute respiratory failure with bilateral infiltrates on chest radiograph, a PaO(2)/FiO(2) ratio < 300 mmHg and extravascular lung water indexed for body weight >/= 12 ml/kg. INTERVENTION: We assessed pulmonary permeability by two indexes obtained from transpulmonary thermodilution: extravascular lung water/pulmonary blood volume (PVPI) and the ratio of extravascular lung water index over global end-diastolic volume index. The cause of pulmonary edema was determined a posteriori by three experts, taking into account medical history, clinical features, echocardiographic left ventricular function, chest radiography findings, B-type natriuretic peptide serum concentration and the time-course of these findings with therapy. Experts were blind for pulmonary permeability indexes and for global end-diastolic volume. MEASUREMENTS AND RESULTS: ALI/ARDS was diagnosed in 36 cases. The PVPI was 4.7+/-1.8 and 2.1+/-0.5 in patients with ALI/ARDS and hydrostatic pulmonary edema, respectively (p<0.05). The extravascular lung water index/global end-diastolic volume index ratio was 3.0 x 10(-2)+/-1.2 x 10(-2) and 1.4 x 10(-2)+/-0.4 x 10(-2) in patients with ALI/ARDS and with hydrostatic pulmonary edema, respectively (p<0.05). A PVPI >/= 3 and an extravascular lung water index/global end-diastolic index ratio >/= 1.8 x 10(-2) allowed the diagnosis of ALI/ARDS with a sensitivity of 85% and specificity of 100%. CONCLUSION: These results suggest that indexes of pulmonary permeability provided by transpulmonary thermodilution may be useful for determining the mechanism of pulmonary edema in the critically ill.

Capillary Permeability↗
PubMed2002

Cl secretagogues reduce basolateral K permeability in the rabbit corneal epithelium.

The stromal-to-tear transport of Cl by the rabbit corneal epithelium is increased by pharmacological effectors (secretagogues) that raise cAMP. It is well established that such secretagogues increase the apical membrane permeability to Cl and thus facilitate the efflux of the anion. However, we and others have found that cAMP-elevating agents frequently decrease the transepithelial potential difference across the rabbit cornea. The mechanism underlying this latter phenomenon had not been characterized. In this report, transepithelial and microelectrode studies were combined with measurements of unidirectional fluxes of 36Cl, 22Na and 86Rb to show that secretagogues known to act via cAMP also decrease the K permeability of the basolateral membrane, which by cellular depolarization would decrease apical Cl secretion. This effect was increasingly pronounced as a function of concentration when agents (e.g., epinephrine, isoproterenol) were applied to the apical side of the preparations. The addition of these agonists to the basolateral bathing solution, or of forskolin to the apical side, solely elicited inhibitions of basolateral K permeability. It seems that apical Cl and basolateral K conductances are independently and inversely regulated by cAMP. The opposite effects that cAMP could have on fluid secretion and epithelial thickness, by increasing apical Cl permeability but decreasing basolateral K permeability, may serve as a mechanism to maintain epithelial thickness within a narrow range.

Animals↗
PubMed2004

Expression of the skate (Raja erinacea) AE1 osmolyte channel in Xenopus laevis oocytes: monovalent cation permeability.

The aim of this study was to express the cloned skate anion exchanger 1 (skAE1) in Xenopus oocytes and determine whether the differences in monovalent cation permeabilities in hypotonically stimulated skate and trout erythrocytes could be due to differences in the presence or absence of intracellular channel regulators between the two species or in the intrinsic permeability properties of the channels themselves. The expressed protein (skAE1) was inserted into the oocyte cell membrane and facilitated both Cl- exchange and taurine transport. Expression of skAE1 in oocytes showed similar monovalent cation permeabilities as previously reported for skate erythrocytes and different from both trout erythrocytes and trAE1 expressed in Xenopus oocytes. These results show that the skAE1 expressed in oocytes functions in a manner similar to that of the osmolyte channel in hypotonically activated skate erythrocytes and supports the hypothesis that differences in the monovalent cation permeabilities of the osmolyte channels in skate and trout RBCs resides in the differences in permeability properties of the channels between the two species.

Animals↗
PubMed2005

Aldosterone reduces crypt colon permeability during low-sodium adaptation.

Fluid and electrolyte absorption by colonic crypts depends on the transport properties of crypt cellular and paracellular routes and of the pericryptal sheath. As a low-Na(+) diet increases aldosterone and angiotensin II secretion, either hormone could affect absorption. Control and adrenalectomized (ADX) Sprague-Dawley rats were kept at a high-NaCl (HS) diet and then switched to low-NaCl (LS) diet for 3 days. Aldosterone or angiotensin II plasma concentrations were maintained using implanted osmotic mini-pumps. The extracellular Na(+) concentration in isolated rat distal colonic mucosa was determined by confocal microscopy using a low-affinity Na(+) -sensitive fluorescent dye (Sodium red, and Na(+) -insensitive BODIPY) bound to polystyrene beads. Crypt permeability to FITC-labelled dextran (10 kDa) was monitored by its rate of escape from the crypt lumen into the pericryptal space. Mucosal ion permeability was estimated by transepithelial electrical resistance (TER) and amiloride-sensitive short-circuit current (SCC). The epithelial Na(+) channel, ENaC, was determined by immunolocalization. LS diet decreased crypt wall permeability to dextran by 10-fold and doubled TER. Following ADX, aldosterone decreased crypt wall dextran permeability, increased TER, increased Na(+) accumulation in the pericryptal sheath and ENaC expression even in HS. Infusion of angiotensin II to ADX rats did not reverse the effects of aldosterone deprivation. These findings indicate that aldosterone alone is responsible for both the increase in Na(+) absorption and the decreased paracellular and pericryptal sheath permeability.

Adaptation, Physiological↗
PubMed2000

Water permeability measurement in living cells and complex tissues.

The identification of molecular water transporters and the generation of transgenic mice lacking water transporting proteins has created a need for accurate methods to measure water permeability. This review is focused on methodology to characterize water permeability in living cells and complex multicellular tissues. The utility of various parameters defining water transport is critically evaluated, including osmotic water permeability (P(f)), diffusional water permeability (P(d)), Arrhenius activation energies (E(a)), and solute reflection coefficients (sigma(p)). Measurements in cellular and complex tissues can be particularly challenging because of uncertainties in barrier geometry and surface area, heterogeneity in membrane transporting properties, and unstirred layer effects. Strategies to measure plasma membrane P(f) in cell layers are described involving light scattering, total internal reflection fluorescence microscopy, confocal microscopy, interferometry, spatial filtering microscopy, and volume-sensitive fluorescent indicators. Dye dilution and fluorescent indicator methods are reviewed for measurement of P(f) across cell and tissue barriers. Novel fluorescence and gravimetric methods are described to quantify microvascular and epithelial water permeabilities in intact organs, using as an example lungs from aquaporin knockout mice. Finally, new measurement strategies and applications are proposed, including high-throughput screening for identification of aquaporin inhibitors.

Animals↗
PubMed2003

Effect of dDAVP on basolateral cell surface water permeability in the outer medullary collecting duct.

We report a novel approach for assessing the volume of living cells which allows quantitative, high-resolution characterization of dynamic changes in cell volume while retaining the cell functionality. The aim of this study was to evaluate the short-term effect of vasopressin on basolateral cell surface water permeability in the outer medullary collecting duct (OMCD). The permeability of the basolateral cell membrane was determined in the tubules where the apical membrane was blocked with oil injected into the lumen. The apparent coefficient of water permeability (Pf) was evaluated by measuring the cell swelling after the step from hypertonic to isotonic medium (600 mosm to 300 mosm). Desmopressin (dDAVP) induced an increase of the basolateral Pf from 113.7+/-8.5 microm/s in control cells to 186.6+/-11.4 mum/s in micro-dissected fragments of the OMCD incubated in vitro (10(-7) M dDAVP, 30 min at 37 degrees C) (P<0.05). Mercury caused pronounced inhibition of basolateral water permeability (26.0+/-6.9 microm/s; P<0.05). The effect of mercury (1.0 mM HgCl2) was reversible: after washing the fragments with PBS for 20 min, Pf values were restored to the control levels (125.0+/-9.5 microm/s). The results of the study indicate the existence of a mechanism controlling the osmotic water permeability of the basolateral cell membrane in the OMCD epithelium.

Animals↗
PubMed2004

Permeability and the hidden area of lipid bilayers.

The passive water permeability of a lipid vesicle membrane was studied, related to the hydrostatic (not osmotic) pressure difference between the inner and the outer side of the vesicle in a water environment without additives. Each pressure difference was created by sucking a vesicle into a micropipette at a given sucking pressure. The part of the membrane sucked into the micropipette (the projection length) was measured as a function of time. The time dependence can be divided into two intervals. We put forward the idea that smoothing of membrane defects, accompanied by an increase of the membrane area, takes place during the initial time interval, which results in a faster increase of the projection length. In the second time interval the volume of the vesicle decreases due to the permeability of its membrane and the increase of the projection length is slower. The hidden area and the water permeability of a typical lipid bilayer were estimated. The measured permeability, conjugated to the hydrostatic pressure difference, is an order of magnitude higher than the known value of the permeability, conjugated to the osmotic pressure difference. A hypothesis, based on pore formation, is proposed as an explanation of this experimental result.

Computer Simulation↗
PubMed2006

Outer membrane mutation effects on UDP-glucose permeability and whole-cell catalysis rate.

In whole-cell biocatalysis, cell envelopes represent a formidable barrier for substrates to permeate. The present research addresses this critical issue by investigating the effects of outer membrane mutation on uridine diphosphate (UDP)-glucose-utilizing enzymes in whole-cell systems. Owing to the severe limitation in substrate permeability, the wild-type Escherichia coli cells only exhibited as low as 4% of available enzyme activities. The reduction of the barriers of the outer membrane permeability (by mutations in its structure) led to a striking acceleration (up to 14-fold) of the reaction rate in cells expressing UDP-glucose dehydrogenase. Mutations in the lipopolysaccharide synthesis pathway or Braun's lipoprotein are both effective. The acceleration was dependent upon the substrate concentrations as well as the enzyme expression level. In addition, the mutation has been demonstrated to be much more effective than the freeze-thaw permeabilizing method. An application of outer membrane mutants was illustrated with the synthesis of a disaccharide (N-acetyllactosamine) from UDP-glucose. Both reaction rate and product yield were enhanced significantly (more than twofold) in the lipoprotein mutant, demonstrating the importance of the outer membrane permeability barrier and the advantages of using outer membrane mutants in synthesis. This research and the results outlined in this paper point to a valid strategy in addressing permeability issues in whole-cell biocatalysis. It also highlights a need for an assessment of substrate permeability in biocatalysis research and development.

Amino Sugars↗
PubMed2003

Increased sucrose permeability in Behçet's disease.

Behçet's disease (BD) is a chronic, relapsing, systemic vasculitis with unknown etiology. During the progression of the disease, gastrointestinal involvement can be observed. The aim of this study was to find out the predictive value of the sucrose permeability test in detecting gastrointestinal mucosal damage in BD. Twenty-six male Behçet's patients and 21 age- and sex-matched controls were enrolled in the study. Seventeen patients had active disease, while nine did not. Active disease was defined as having elevated erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) levels or at least two of the diagnostic criteria in the previous month. Patients and controls were investigated with the upper gastrointestinal permeability test. Of all the patients, 25 were investigated endoscopically. The urine sucrose levels were significantly higher in patients than in the control group (P = 0.0001) and in patients with active disease than those with inactive disease (P < 0.0001), while urine sucrose of patients with inactive disease and the control group did not differ. The endoscopic findings were not specific to BD. Active and inactive BD had similar endoscopic findings. Increased upper gastrointestinal permeability was established in patients with BD. This increased permeability was not related to a specific gastrointestinal BD lesion. Further studies with larger series must be performed in order to determine the value of the sucrose permeability test in detecting mucosal involvement in BD.

Adolescent↗
PubMed1996

The effect of TNF-alpha and IL-6 on the permeability of the rat blood-retinal barrier in vivo.

The blood-retinal barrier (BRB), which is formed by the retinal vascular endothelium and the retinal pigment epithelium, is responsible for controlling the passage of cells and molecules into the neuroretina. During ocular inflammatory diseases, however, this selective control is altered due to changes in BRB function such as increased permeability and leucocyte recruitment. The causative factors leading to barrier breakdown are not entirely understood although cytokines have recently been implicated. We have investigated the effect of the cytokines tumour necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) upon the integrity of the rat BRB. Lewis rats received a dose of each cytokine by intravitreal injection and the permeability of the BRB was assessed using the smaller molecular weight vascular tracer 14C mannitol. A significant opening of the barrier to mannitol was detected following an intravitreal injection of 2 x 10(4) U of TNF-alpha which persisted from day 1 to day 5 post-injection (PI). The permeability of the BRB returned to normal values by day 7 PI. Only occasional mononuclear inflammatory cells were seen in the retina and vitreous of the TNF-alpha-treated eyes although they remained in evidence up to day 5 PI. In the TNF-alpha-infected eye there was immunohistological evidence of activation of tissue-resident cells, particularly in the inner plexiform layer. Of particular interest was the observation that the BRB of the non-injected contralateral eye also exhibited increased permeability over a similar time-course but without any evidence of cellular infiltration or activation of tissue-resident cells. Unlike TNF-alpha, the administration of 1 x 10(3) U of IL-6 into the vitreous caused no measurable increase in BRB permeability despite inducing a small infiltration of inflammatory cells.

Animals↗
PubMed2005

Nucleotide regulation of paracellular Cl- permeability in natural rabbit airway epithelium.

In this study, we demonstrate a novel regulatory mechanism by which mucosal nucleotides via P2Y receptors decrease paracellular Cl(-) ion permeability in natural rabbit airway epithelium (in addition to a decrease in active Na(+) absorption). In contrast to primary cultures, the natural airway epithelium is a low-resistance epithelium, and an equivalent circuit model predicts that changes of more than approximately 12% in transepithelial conductance (G (t)) must include an effect on paracellular conductance (G (s)). Mucosal P2Y receptor stimulation with uridine triphosphate (UTP; 200 microM) decreased G (t) by up to 50% (average, 24%) and simultaneously decreased the paracellular Cl(-) permeability (mucosa-to-serosa Cl(-) flux) by 16%, but had no effect on mannitol permeability. The G (t) response to UTP was mimicked and attenuated by ionomycin (1 microM), suggesting a dependence on Ca(2+) (i). Amiloride (100 microM) and hyperosmolarity (+75 mM mannitol) also decreased G (t), indicating a role of cell shrinkage. Elevation of cAMP with forskolin (8 microM) or isoproterenol (10 microM) increased G (t) by 55 and 32%, and forskolin increased paracellular Cl(-) permeability by 37% without affecting mannitol permeability. The opposite effects of Ca(2+) (i) and cAMP on G (t) suggest an autocrine nucleotide signaling sequence where P2Y-dependent decrease in passive, paracellular Cl(-) transport is succeeded by a reversion of this effect due to P1-receptor-stimulated cAMP formation by adenosine originating from a time-dependent breakdown of mucosal ATP.

Adenylyl Cyclases↗
PubMedDate not supplied

AVP-independent high osmotic water permeability of frog urinary bladder and autacoids.

In the isolated frog urinary bladder a 20- to 50-fold increase of the osmotic water permeability has been revealed in the absence of arginine vasopressin (AVP) as a result of several successive changes of the serosal Ringer solution. This increase of the osmotic water permeability was of the same magnitude as that of the effect of 1 nM AVP. Similarly to the effect of AVP, the amount of adenosine 3',5'-cyclic monophosphate (cAMP) in the cells rose, and aggregates of intramembraneous particles were formed in the apical plasma membrane of granular cells (as shown by the freeze-fracture method). Immunocytochemical studies using anti-actin monoclonal antibodies indicated depolymerization of F-actin following the AVP-independent change in water permeability. It was possible to decrease the high level of osmotic permeability to the initial level if 10 microl/ml of frog blood serum or a lipid extract of this blood serum, or 1 microM arachidonic acid or 1 nM prostaglandin E2 was added to the serosal Ringer solution. The rapid restoration of the osmotic water impermeability of the epithelium after the AVP- evoked effect was achieved by the addition to the serosal Ringer solution of Ringer solution in which intact frog urinary bladders had been previously incubated for 1 h. The data obtained indicate that the maintenance of the impermeability to water of the osmoregulating epithelium and the restoration of the initial low level of the osmotic permeability after the effect of AVP are due to participation of prostaglandin E2 and other autacoids as well as, probably, some physiologically active substances of a lipid nature that are present in the blood serum.

Animals↗
PubMed1998

Echinococcus granulosus: membrane permeability of secondary hydatid cysts to albendazole sulfoxide.

The objectives of the present study were, first, to establish a methodology for evaluation of the permeability in vitro of hydatid cysts to different drugs and, second, to compare the permeability to albendazole sulfoxide of cysts from untreated animals, cysts from animals treated with 50 mg/kg netobimin for 5 days, and cysts from animals treated with 50 mg/kg netobimin plus 1.1 mg/kg fenbendazole for 5 days. The drug flow follows the Fick law, i.e., the uptake occurs by simple diffusion. We calculated the permeability constant of the cyst membrane by taking into account the disappearance velocity constant, the cyst area, and the incubation solution volume. The permeability value obtained for albendazole sulfoxide was 8.06+/-2.30 x 10(-6) cm s(-1) in cysts from untreated animals, 5.56+/-2.53 x l0(-6) cm s(-1) in cysts from animals treated with netobimin, and 7.05+/-3.04 x 10(-6) cm s(-1) in cysts from animals treated with netobimin +/- fenbendazole. These permeability values show significant differences (P < 0.05).

Albendazole↗
PubMed2004

Effects of intestinal surgery on pulmonary, glomerular, and intestinal permeability, and its relation to the hemodynamics and oxidative stress.

PURPOSE: To investigate the pattern of changes of gut mucosal, glomerular, and pulmonary permeability in response to major resectional intestinal surgery, and to evaluate whether these changes are related to oxidative stress. METHODS: Eight patients undergoing elective intestinal surgery. Lactulose/mannitol ratio (LMR), urinary albumin/creatinine ratio (MACR), and extravascular lung water and its ratio to intrathoracic blood volume (EVLW/ITBV) were measured preoperatively and at different time points postsurgery. The oxidant/antioxidant balance was assessed by measuring thiobarbituric acid-reactive species, reduced glutathione, plasma total antioxidant capacity, superoxide dismutase, and glutathione peroxidase. RESULTS: Uncomplicated intestinal surgery was associated with early increase in LMR and MACR. The EVLW/ITBV ratio increased, but still remained within the normal range. The amount of EVLW was not affected. While renal permeability changes resolved rapidly, increased intestinal permeability persisted longer postoperatively. There was no evidence for any marked disturbances in the oxidant/antioxidant balance. CONCLUSIONS: This pilot study indicated that a moderate increase in gut and renal permeability, even in the absence of clinical sequelae, is an early feature of uncomplicated intestinal surgical trauma. These alterations are not accompanied by any clinically detectable changes in pulmonary permeability.

Adult↗
PubMed1982

Long-term effects of captopril on passive sodium permeability and contractility in vascular smooth muscles of spontaneously hypertensive rats.

Long-term effects of captopril on passive sodium permeability and cellular sodium concentration in the aorta of spontaneously hypertensive rats were examined in terms of contractile properties of the muscle. In cold lithium solution, cellular sodium in the aorta isolated from spontaneously hypertensive rats leaked more rapidly than did that isolated from Wistar Kyoto rats (WKY), suggesting an increased sodium permeability in the aorta of spontaneously hypertensive rats. Six weeks of treatment with captopril reduced the increased sodium permeability after hydralazine had failed. Inhibition of the sodium pump by incubating the aorta in potassium-free solution produced a slowly developing contraction which was associated with accumulation of cellular sodium. Both the magnitude of contraction and the accumulation of sodium during exposure to potassium-free solution for 1 hour were significantly less in the aorta isolated from spontaneously hypertensive rats treated with captopril compared with those from control spontaneously hypertensive rats. These data suggest that after prolonged administration, captopril alters the abnormal sodium permeability of vascular smooth muscle in spontaneously hypertensive rats and that the restoration of normal permeability reduces vascular tone.

Animals↗
PubMed1977

Factors determining human chorion laeve permeability in vitro.

An increased mean diffusion permeability across human chorion laeve in vitro was measured for meperidine (D = 5.26 x 10(-6) cm.2 sec.-1) and diazepam (D = 4.51 X 10(-6) cm.2 sec.-1). These values corresponded to large chloroform-buffer partition coefficients (49 and 29) measured for these two compounds. Diffusion permeability values of 3.98 and 2.18 x 10-6 cm.2 sec.-1 measured for urea and glucose corresponded to their relative insolubility in lipid, as indicated by chloroform-buffer partition coefficients of 0.05 and 0.0004, respectively. An increase in placental permeability in vitro to the weak organic acid 5,5-dimethyl, 2,4-oxazalidinedione at lower pH's corresponded to an increase in the fat-soluble nonionized fraction of this compound. These data support the concept that this tissue is most permeable to compounds of relatively small molecular size and/or with a high level of lipid solubility. The large diffusion permeability values measured for meperidine and diazepam suggest that these compounds will diffuse rapidly between mother and fetus at a maximal rate limited only by uterine blood flow.

Cell Membrane Permeability↗
PubMed1991

The effects of storage after extraction of the teeth on human dentine permeability in vitro.

Freshly extracted third molars were stored for one week in one of four solutions: 70% ethanol, 10% formalin, distilled water with thymol and phosphate-buffered saline with thymol. Crown segments were prepared and initial permeability measurements taken. Each specimen was placed in a fresh preparation of its original solution, and permeability was measured over two periods: 1, 4, 6 and 8 days or 1, 8, 15 and 22 days. Ten crown segments were used for each solution for each time sequence. Permeabilities were lower for those specimens stored in ethanol and formalin than in water/thymol and saline/thymol, but most specimens showed increased permeability with time. Both storage solution and storage time had statistically significant effects (p less than 0.05), with significant differences between specimens stored in water/thymol and saline/thymol and those stored in ethanol and formalin. Thus, type of storage solution effects dentine permeability over time.

Analysis of Variance↗
PubMed1977

Polyol permeability of the human red cell. Interpretation of glucose transport in terms of a pore.

The kinetic equations describing transport through a pore that has a binding site and that undergoes a conformational change are identical to those of a carrier model. Therefore, in order to distinguish between the two models it is necessary to test specific predictions based on detailed mechanistic models. A pore model is described in which the substrate (glucose) is able to reach the single binding site only from the outside when the pore is in conformation I and only from the inside when it is conformation II. On the basis of this model it is predicted that solutes which do not have any specific affinity for the binding site should still have a finite permeability via the glucose transport system if they are the same size or smaller than glucose. This permeability should be proportional to the volume of distribution of the solute in the pore and should therefore decrease with increasing molecular size. A geometric pore volume can be estimated from this size dependence. In order to test these predictions, the glucose-dependent permeability of a series of 4-carbon (erythritol), 5-carbon (D-arabitol, L-arabitol and xylitol) and 6-carbon (D-mannitol, D-sorbitol and myo-inositol) polyols was measured. The permeability of all the polyols is decreased by the presence of glucose and the KI of this "inhibitable" component is similar to that D-sorbose, suggesting that this component is associated with the glucose transport system. Since these observations could be explained entirely in terms of a specific affinity for a carrier binding site, they do not exclude a carrier mechanism. However, as predicted for the pore model, this "inhibitable" permeability decreased with increasing molecular size and the calculated geometric pore volume was of a size that would be expected for a cell membrane pore.

Binding, Competitive↗