Model Of Epithelial Transport Research Articles

Predicting sex differences in the effects of diuretics in renal epithelial transport during angiotensin II-induced hypertension.

Chronic angiotensin II (ANG II) infusion is an experimental model that induces hypertension in rodents. The natriuresis, diuresis, and blood pressure responses differ between males and females. This is perhaps not unexpected, given the rodent kidney, which plays a key role in blood pressure regulation, exhibits marked sex differences. Under normotensive conditions, compared with males, the female rat nephron exhibits lower Na+/H+ exchanger 3 (NHE3) activity along the proximal tubule but higher Na+ transporter activities along the distal segments. ANG II infusion-induced hypertension induces a pressure natriuretic response that reduces NHE3 activity and shifts Na+ transport capacity downstream. The goals of this study were to apply a computational model of epithelial transport along a rat nephron 1) to understand how a 14-day ANG II infusion impacts segmental electrolyte transport in male and female rat nephrons and 2) to identify and explain any sex differences in the effects of loop diuretics, thiazide diuretics, and K+-sparing diuretics. Model simulations suggest that the NHE3 downregulation in the proximal tubule is a major contributor to natriuresis and diuresis in hypertension, with the effects stronger in males. All three diuretics are predicted to induce stronger natriuretic and diuretic effects under hypertension compared with normotension, with relative increases in sodium excretion higher in hypertensive females than in males. The stronger natriuretic responses can be explained by the downstream shift of Na+ transport load in hypertension and by the larger distal transport load in females, both of which limit the ability of the distal segments to further elevate their Na+ transport.NEW & NOTEWORTHY Sex differences in the prevalence of hypertension are found in human and animal models. The kidney, which regulates blood pressure, exhibits sex differences in morphology, hemodynamics, and membrane transporter distributions. This computational modeling study provides insights into how the sexually dimorphic responses to a 14-day angiotensin II infusion differentially impact segmental electrolyte transport in rats. Simulations of diuretic administration explain how the natriuretic and diuretic effects differ between normotension and hypertension and between the sexes.

Reproducibility study of the modular and reusable model of epithelial transport in the proximal convoluted tubule

We describe here our implementation of a renal epithelial model as published in Noroozbabaee et al., 2022. The flexible and modular model we presented in the current work can be adapted to specific configurations of epithelial transport. The model describes the cellular and subcellular mechanisms of the transporters, intracellular buffering, solute fluxes, and other processes. We provide free and open access to the Python implementation to ensure our multiscale proximal tubule model is accessible, enabling the reader to explore the model through configuring their own simulations, executing reproducibility tests and sensitivity analyses, and reusing the model in new work. Here we present the reproduction of a selection of results from Noroozbabaee et al., 2022, providing readers with brief instructions on using the Python implementation to produce these results from the primary article.

Reproducibility study of the modular and reusable model of epithelial transport in the proximal convoluted tubule

We describe here our implementation of a renal epithelial model as published in Noroozbabaee et al., 2022. The flexible and modular model we presented in the current work can be adapted to specific configurations of epithelial transport. The model describes the cellular and subcellular mechanisms of the transporters, intracellular buffering, solute fluxes, and other processes. We provide free and open access to the Python implementation to ensure our multiscale proximal tubule model is accessible, enabling the reader to explore the model through configuring their own simulations, executing reproducibility tests and sensitivity analyses, and reusing the model in new work. Here we present the reproduction of a selection of results from Noroozbabaee et al., 2022, providing readers with brief instructions on using the Python implementation to produce these results from the primary article.

Reproducibility study of the modular and reusable model of epithelial transport in the proximal convoluted tubule

We describe here our implementation of a renal epithelial model as published in Noroozbabaee et al., 2022. The flexible and modular model we presented in the current work can be adapted to specific configurations of epithelial transport. The model describes the cellular and subcellular mechanisms of the transporters, intracellular buffering, solute fluxes, and other processes. We provide free and open access to the Python implementation to ensure our multiscale proximal tubule model is accessible, enabling the reader to explore the model through configuring their own simulations, executing reproducibility tests and sensitivity analyses, and reusing the model in new work. Here we present the reproduction of a selection of results from Noroozbabaee et al., 2022, providing readers with brief instructions on using the Python implementation to produce these results from the primary article.

Reproducibility study of the modular and reusable model of epithelial transport in the proximal convoluted tubule

We describe here our implementation of a renal epithelial model as published in Noroozbabaee et al., 2022. The flexible and modular model we presented in the current work can be adapted to specific configurations of epithelial transport. The model describes the cellular and subcellular mechanisms of the transporters, intracellular buffering, solute fluxes, and other processes. We provide free and open access to the Python implementation to ensure our multiscale proximal tubule model is accessible, enabling the reader to explore the model through configuring their own simulations, executing reproducibility tests and sensitivity analyses, and reusing the model in new work. Here we present the reproduction of a selection of results from Noroozbabaee et al., 2022, providing readers with brief instructions on using the Python implementation to produce these results from the primary article.

Reproducibility study of the modular and reusable model of epithelial transport in the proximal convoluted tubule

We describe here our implementation of a renal epithelial model as published in Noroozbabaee et al., 2022. The flexible and modular model we presented in the current work can be adapted to specific configurations of epithelial transport. The model describes the cellular and subcellular mechanisms of the transporters, intracellular buffering, solute fluxes, and other processes. We provide free and open access to the Python implementation to ensure our multiscale proximal tubule model is accessible, enabling the reader to explore the model through configuring their own simulations, executing reproducibility tests and sensitivity analyses, and reusing the model in new work. Here we present the reproduction of a selection of results from Noroozbabaee et al., 2022, providing readers with brief instructions on using the Python implementation to produce these results from the primary article.

Epithelial Modelling Platform: A Tool for Investigating Hypothesis through Discovery and Assembly of Computational Models of Epithelial Transport

Scientists often leverage computational models of biological systems to investigate hypotheses which are difficult or prohibitively expensive to achieve experimentally. Such investigations are best achieved by utilizing suitable computational models, reusing existing validated models where possible and creating novel models consistently as needed. This requires tools which enable the discovery and exploration of existing models matched with assistance in constructing and testing new models. Enabling scientists or clinicians to use such a tool by describing their requirements in a manner familiar to themselves greatly improves the accessibility of the tool. We have developed a web-based tool, the Epithelial Modelling Platform, for scientists and clinicians to discover relevant models and then assemble these into a novel model customized for investigating their hypotheses. While our tool specifically focuses on epithelial transport, by utilizing relevant community standards and publicly accessible knowledge repositories, it is extensible to other areas of application. The platform abstracts underlying mathematics of the computational models and provides a visual environment which mimics biological phenomena of an epithelial cell. Beyond the mathematical models, we have implemented a feature to discover existing simulation experiments which match the features of the novel models users create. By executing these simulation experiments with the novel models and comparing to previous model predictions and/or experimental or clinical observations we are able to provide the user with some measure of verification that their model matches, or doesn't match, existing knowledge captured in the various repositories utilized. Support or Funding Information Supported by the Medical Technologies Center of Research Excellence (MedTech CoRE), the Aotearoa Foundation, and the Auckland Bioengineering Institute Model discovery interface to search for models in the Physiome Model Repository (PMR) which are relevant to the query “flux of sodium”. By querying the biological knowledge stored in PMR the Epithelial Modelling Paltform retrieves components from the weinstein, mackenzie, and chang fujita models. Illustrating a similarity between weinstein and mackenzie model. In this case both models have similar compartment labeled with a unique color. An instance of the Epithelial Modelling Platform. It consists of five compartments and three membranes. Biological processes have been represented with various shapes: fluxes with circles; channels with polygons; and diffusive fluxes with a text, a line, and an arrow. On the right, check boxes have been generated for the visualized shapes on the membranes to allow the user to drag and drop. Concentration of the biological description of CellML variables float in the respective compartments. A suggestion window based on the biological description in the Physiome Model Repository when a circle, represented as flux of Na+ in the weinstein model, is moved from apical to basolateral membrane. A model verification instance for testing components of an assembled epithelial model reproduce the same simulation experiment. A model verification instance for testing components of an assembled epithelial model reproduce the same simulation experiment. A spider chart to find similarity of models with respect to an assembled epithelial model. This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Stationary and Nonstationary Ion and Water Flux Interactions in Kidney Proximal Tubule: Mathematical Analysis of Isosmotic Transport by a Minimalistic Model.

Our mathematical model of epithelial transport (Larsen et al. Acta Physiol. 195:171-186, 2009) is extended by equations for currents and conductance of apical SGLT2. With independent variables of the physiological parameter space, the model reproduces intracellular solute concentrations, ion and water fluxes, and electrophysiology of proximal convoluted tubule. The following were shown: 1. Water flux is given by active Na+ flux into lateral spaces, while osmolarity of absorbed fluid depends on osmotic permeability of apical membranes. 2. Following aquaporin "knock-out," water uptake is not reduced but redirected to the paracellular pathway. 3. Reported decrease in epithelial water uptake in aquaporin-1 knock-out mouse is caused by downregulation of active Na+ absorption. 4. Luminal glucose stimulates Na+ uptake by instantaneous depolarization-induced pump activity ("cross-talk") and delayed stimulation because of slow rise in intracellular [Na+]. 5. Rate of fluid absorption and flux of active K+ absorption would have to be attuned at epithelial cell level for the [K+] of the absorbate being in the physiological range of interstitial [K+]. 6. Following unilateral osmotic perturbation, time course of water fluxes between intraepithelial compartments provides physical explanation for the transepithelial osmotic permeability being orders of magnitude smaller than cell membranes' osmotic permeability. 7. Fluid absorption is always hyperosmotic to bath. 8. Deviation from isosmotic absorption is increased in presence of glucose contrasting experimental studies showing isosmotic transport being independent of glucose uptake. 9. For achieving isosmotic transport, the cost of Na+ recirculation is predicted to be but a few percent of the energy consumption of Na+/K+ pumps.

Investigating Hypotheses through Discovery of Relevant Models of Epithelial Transport

Scientists often utilize computational models to help understand experimental observations or to investigate hypotheses in ways that are not practically achievable experimentally. The first step in constructing such models is to discover existing models which can be reused to help in such an investigation. We are developing novel research tools to enable the discovery and exploration of computational models relevant to specific research questions or hypotheses. This can aid biologists and clinicians to test their clinical or experimental hypotheses from a given collection of disparate mechanisms and/or observations such as diseases, drug actions and clinical observations.Computational tools and standards have evolved over the years such as CellML to encode mathematical models of biological systems; SemGen to annotate models; and the Physiome Model Repository (PMR) to store these models and their comprehensive descriptions to ensure the deposited knowledge is persistent, identifiable, discoverable and sharable. Our long term goal is to develop a knowledge management system capable of constructing multi‐scale renal nephron models from information extracted from PMR to investigate transport phenomena in the kidney at the cellular and subcellular level and the impact on nephron function.We have used the SemGen tool to comprehensively annotate a preliminary cohort of renal epithelial transport models available in PMR to provide the initial knowledgebase for model discovery and exploration, and in particular, to extract a model suitable for testing specific clinical or experimental hypotheses. One use of such exploration is the identification of missing resource(s), which could be addressed via more accurate description of existing resources or the addition of new resource to the repository.Specifically, we present here a web‐based tool enabling scientists to discover and explore epithelial transport models that are relevant to their specific research questions. Biologists and clinicians can use this tool to discover models with specific transport proteins, solute species, genes, anatomical location, or other relevant information. The result of this discovery is a “recipe” describing the computational model that can be assembled to help the user investigate their hypothesis.Support or Funding InformationSupported by the MedTech Centre of Research ExcellenceThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Predicted effect of circadian clock modulation of NHE3 of a proximal tubule cell on sodium transport.

Major renal functions such as renal blood flow, glomerular filtration rate, and urinary excretion are known to exhibit circadian oscillations. However, the underlying mechanisms that govern these variations have yet to be fully elucidated. To better understand the impact of the circadian clock on renal solute and water transport, we have developed a computational model of the renal circadian clock and coupled that model to an epithelial transport model of the proximal convoluted cell of the rat kidney. The activity of the Na+-H+ exchanger 3 (NHE3) is assumed to be regulated by changes in transcription of the NHE3 mRNA due to regulation by circadian clock proteins. The model predicts the rhythmic oscillations in NHE3 activity, which gives rise to significant daily fluctuations in Na+ and water transport of the proximal tubule cell. Additionally, the model predicts that 1) mutation in period 2 (Per2) or cryptochrome 1 (Cry1) preserves the circadian rhythm and modestly raises Na+ reabsorption; 2) mutation in Bmal1 or CLOCK eliminates the circadian rhythm and modestly lowers Na+ reabsorption; 3) mutation in Rev-Erb or ROR-related orphan receptor (Ror) has minimal impact on the circadian oscillations. The model represents the first step in building a tool set aimed at increasing our understanding of how the molecular clock affects renal ion transport and renal function, which likely has important implications for kidney disease.

Renal potassium handling in rats with subtotal nephrectomy: modeling and analysis.

We sought to decipher the mechanisms underlying the kidney's response to changes in K+ load and intake, under physiological and pathophysiological conditions. To accomplish that goal, we applied a published computational model of epithelial transport along rat nephrons in a sham rat, an uninephrectomized (UNX) rat, and a 5/6-nephrectomized (5/6-NX) rat that also considers adaptations in glomerular filtration rate and tubular growth. Model simulations of an acute K+ load indicate that elevated expression levels and activities of Na+/K+-ATPase, epithelial sodium channels, large-conductance Ca2+-activated K+ channels, and renal outer medullary K+ channels, together with downregulation of sodium-chloride cotransporters (NCC), increase K+ secretion along the connecting tubule, resulting in a >6-fold increase in urinary K+ excretion in sham rats, which substantially exceeds the filtered K+ load. In the UNX and 5/6-NX models, the acute K+ load is predicted to increase K+ excretion, but at significantly reduced levels compared with sham. Acute K+ load is accompanied by natriuresis in sham rats. Model simulations suggest that the lesser natriuretic effect observed in the nephrectomized groups may be explained by impaired NCC downregulation in these kidneys. At a single-nephron level, a high K+ intake raises K+ secretion along the connecting tubule and reabsorption along the collecting duct in sham, and even more in UNX and 5/6-NX. However, the increased K+ secretion per tubule fails to sufficiently compensate for the reduction in nephron number, such that nephrectomized rats have an impaired ability to excrete an acute or chronic K+ load.

Transport in technicolor: The sea urchin embryo as an epithelial transport model system

Transport in technicolor: The sea urchin embryo as an epithelial transport model system

Assessment of the retinal pigment epithelial functions‐ modelling approach

AbstractPurpose Our purpose is to construct mathematical models of functions of retinal pigment epithelium (RPE). Here we show the development and results of two models: 1) a compartmental model of Ca2+ dynamics 2) finite element model of epithelial transport and trans‐epithelial resistance.Methods A model of Ca2+ dynamics of APRE‐19 cells based on an experimental data and literature was constructed. Ca+2 dynamics of APRE‐19 cells were recorded using fluorescent microscope after mechanical stimulation. Various Ca+2 functional conditions were tested. The computational model constructed (Matlab SimBiology ) comprises over 40 cell function parameters and twelve variables ranging from stretch‐sensitive ion channels to ryanodine receptor dynamics and sarco/endoplasmic reticulum ATPases. Further, a model of RPE epithelia barrier was developed based on finite element modelling (FEM) of the epithelia and trans‐epithelial resistance simulating the spatial distribution of epithelial properties originating of the tight junction distribution on epithelia.Results The Ca+2 kinetics model of RPE was able to reproduce the Ca+2 dynamics of APRE cells with high accuracy with above 0.97 cross‐correlation. Further, including stretch‐sensitive ion channels explained the Ca+2 dynamics of the cells close to the mechanically stimulated cell. The epithelial model showed that epithelial inhomogeneity may play a crucial role in epithelial tightness and even very small cellular changes produce large variation on the measures of the epithelial properties.Conclusion The models constructed provide new insight of the functions of the RPE with applications from drug transport studies to assessment of the functionality of stem cell derived RPE.

Response to Field

We read with interest the commentary (1) accompanying our article (2) in the October issue of the JCI. We appreciate Michael Field’s opinion that based on our data, the concept of secretory diarrhea must be revised to include the idea that net water secretion, or diarrhea, can occur in the absence of active ion secretion. However, we disagree with his conclusion that TNF must affect capillary permeability or smooth muscle contractility to generate increased interstitial pressure and a hydraulic driving force for water secretion. In contrast to Field’s suggestion, our study of 2 TNF superfamily members, TNF and LIGHT (lymphotoxin-like inducible protein that competes with glycoprotein D for herpesvirus entry mediator on T cells), demonstrates that water secretion occurs as a consequence of epithelial Na+ malabsorption and increased epithelial paracellular permeability. This is supported by the observation that although TNF and LIGHT cause quantitatively similar paracellular permeability increases, only TNF causes diarrhea. The key difference that accounts for this is that only TNF activates PKCα, thereby inhibiting Na+/H+ exchanger isoform 3 (NHE3); TNF did not induce diarrhea when PKCα-mediated NHE3 inhibition was prevented by either pharmacological inhibitors or PKCα knockout. Could these approaches to PKCα inhibition have also prevented PKCα-dependent changes in capillary permeability or smooth muscle contractility? To test this we took advantage of the observation that LIGHT does not activate PKCα. LIGHT did cause diarrhea when PKC was activated pharmacologically, confirming that LIGHT was fully able to recapitulate TNF-like diarrhea when coupled with PKC activation. More importantly, direct NHE3 inhibition, either pharmacological or genetic, showed that this was the critical second component necessary for LIGHT to cause diarrhea. This was not due to inhibition of endothelial or smooth muscle NHE3, since neither tissue expresses NHE3. The unmistakable conclusion is that the necessary role of PKCα in TNF-induced diarrhea is to inhibit epithelial NHE3 and not to effect changes in capillary permeability or smooth muscle contractility. Why, then, is NHE3 so critical? Is it simply that Na+ absorption provides an osmotic driving force for water absorption? This alone is an inadequate explanation, as inhibition of absorption is not necessarily equivalent to induction of secretion. We propose that loss of NHE3-mediated Na+ absorption results in dissipation of the normal hyperosmolarity of the upper villus that drives water absorption (3). It then follows that increased paracellular permeability allows Na+ to leak from tissue to lumen; without NHE3, Na+ cannot be reabsorbed. Increased epithelial paracellular permeability may also allow water and other solutes to flow into the lumen, thereby compounding loss of the villous osmotic gradient that drives water absorption. In terms of absorption, the model gains further support from the observation that LIGHT-induced increases in permeability enhance water absorption (when NHE3 is active). Thus, this model fully explains the data without the need to invoke increased interstitial pressure to force water through paracellular or transcellular water channels. Is it therefore impossible for elevated interstitial pressure, secondary to increased capillary permeability or smooth muscle contraction, to contribute to TNF-induced diarrhea? It is not. However, if elevated venous or interstitial pressure were able to cause diarrhea by the mechanism proposed by Yablonski and Lifson (4) that is cited by Field (1), it is surprising that diarrhea is not a common clinical characteristic of patients with portal hypertension and that jejunal water and electrolyte transport are normal in these patients (5). We therefore conclude that TNF causes acute diarrhea via myosin light chain kinase–dependent increases in epithelial paracellular permeability coupled with PKCα-dependent NHE3 inhibition. Although intriguing as a hypothesis, no data support the role of increased interstitial pressure physically squeezing water into the lumen as proposed by Field. However, existing models of epithelial transport do provide an ample explanation for the observed synergy between increased epithelial paracellular permeability and Na+ malabsorption.

Potential Difference Measurements of Ocular Surface Na+Absorption Analyzed Using an Electrokinetic Model

Corneal and conjunctival epithelia are capable of transcellular Na+ absorption and Cl- secretion, which drives water movement across these tissues. A recent study demonstrated with a new open-circuit potential difference (PD) technique that Cl- moves across the ocular surface in mice through Ca2+- and cAMP-sensitive Cl- channels, the latter pathway being the cystic fibrosis (CF) transmembrane conductance regulator (CFTR). The purpose of the present study was to identify transporting mechanisms involved in Na+ absorption and to develop a mathematical model of ocular surface ion transport to quantify the relative magnitudes of and electrochemical coupling among transporting processes. PDs across the fluid-bathed ocular surface were measured in anesthetized wild-type and CF mice in response to Na+, Cl-, and K+ ion substitution and transporter agonists, inhibitors, and substrates. An electrokinetic model of the ocular surface epithelium was developed to simulate PD measurements, which involved computation of membrane potentials and cell [Na+], [K+], [Cl-] and volume from transporter activities and extracellular ion concentrations. Na+ replacement produced a 6 +/- 2-mV depolarization that was blocked by amiloride (K(i) 0.8 microM) and benzamil (Ki 0.2 microM). The Na+-dependent depolarization by amiloride was significantly greater in CF mice (19 +/- 3 mV). In wild-type mice, D-, but not L-glucose produced a phloridzin-sensitive, 4.1-mV hyperpolarization in the presence of Na+ and amiloride, with a Km for D-glucose of 2.5 mM. Glycine and L-arginine also produced Na+-dependent hyperpolarizations. The epithelial transport model accurately reproduced experimental PD measurements. PD measurements coupled with model computations defined quantitatively the roles of Na+ and Cl- transport processes in ocular surface ion and fluid secretion, and indicated that CFTR-dependent changes in apparent epithelial Na+ channel (ENaC) activity could be accounted for by electrochemical coupling, without requiring ENaC-CFTR interactions. The data and modeling also predicted significant enhancement of ocular surface fluid secretion by ENaC inhibitors and CFTR activators as possible therapies for dry eye syndromes.

Themes in ion pump regulation.

The Na,K-ATPase is an ion pump present in the plasma membrane. It is of vital importance for cell and body homeostasis and as such is under strict hormonal control. The molecular basis for the acute regulation of Na,K-ATPase is multisite phosphorylation by protein kinases that can alter its behavior. This includes direct effects on the Na,K-ATPase activity, regulation by membrane trafficking, and even dynamic regulation of interaction with regulatory proteins. In shark Na,K-ATPase, the latter includes functional interaction with a small hydrophobic protein of the FXYD protein family, phospholemman-like protein from shark, PLMS. This article summarizes our recent work on the mechanisms involved in the acute regulation of the Na,K-ATPase studied using a plasma membrane preparation from shark salt glands as an epithelial transport model.

Hans Ussing, experiments and models.

The article describes work and impact of Hans H. Ussing, a founder of epithelial physiology. Emphasis is on Ussing's model of epithelial transport, which showed early how a complex function can arise from a few basic principles. The KJU-model was developed 1958 for the amphibian epidermis and later applied and adapted to many epithelia, but especially to those that express amiloride-sensitive sodium channels in their apical membrane. Some of the subsequent research dealing with such channels and their cellular environment is briefly reviewed. The ideas of Hans Ussing were and are an inspiration to many of us, who continue to work in the way Ussing has taught us.

Mechanisms and regulation of ion transport in adult mammalian alveolar type II pneumocytes

The adult alveolar epithelium consists of type I and type II (ATII) pneumocytes that form a tight barrier, which severely restricts the entry of lipid-insoluble molecules from the interstitial to the alveolar space. Current in vivo and in vitro evidence indicates that the alveolar epithelium is also an absorptive epithelium, capable of transporting Na+ from the alveolar lumen, which is bathed by a small amount of epithelial lining fluid, to the interstitial space. The in situ localization of Na(+)-K(+)-ATPase activity in ATII cells and the fact that these cells are involved in a number of crucial functions, such as surfactant secretion and alveolar remodeling after injury, led investigators to examine their transport characteristics. Radioactive flux studies, in both freshly isolated and cultured cells, and bioelectric measurements in ATII cells grown on porous supports indicate that they transport Na+ according to the Koefoed-Johnsen and Ussing model of epithelial transport. Na+ enters the apical membrane, because of the favorable electrochemical gradient, through Na+ cotransporters, a Na(+)-H+ antiport, and cation channels and is pumped across the basolateral membrane by a ouabain-sensitive Na(+)-K+ pump. Na+ transport is enhanced by substances that increase intracellular adenosine 3',5'-cyclic monophosphate. In addition to Na+ transporters, ATII cells contain several transporters that regulate their intracellular pH, including a H(+)-ATPase, which may explain the low pH of the epithelial lining fluid. The absorptive properties of ATII cells may play an important role in regulating the degree of alveolar fluid in health and disease.

Characterization of the human colon carcinoma cell line (Caco-2) as a model system for intestinal epithelial permeability

Caco-2 cells develop morphologic characteristics of normal enterocytes when grown on plastic dishes or nitrocellulose filters. The purpose of this study was to determine whether Caco-2 cells undergo similar differentiation when grown on Transwell polycarbonate membranes, and to study the suitability of Caco-2 monolayers as an intestinal epithelial transport model system. Transepithelial electrical resistance values after confluence were 173.5 Ω · cm2 and remained unchanged through day 17. Permeabilities to the water-soluble fluid-phase markers that do not permeate the membrane, Lucifer yellow CH, [14C]inulin, [14C]polyethylene glycol, and [3H] dextran were < 0.25% of the administered amount per hour after day 10. Qualitative evaluation of uptake and permeability to horseradish peroxidase confirmed the similarity in uptake and barrier properties between this cell system and the small intestinal epithelial layer. We conclude that Caco-2 cells grown on collagen-coated polycarbonate membranes should represent a valuable transport model system for the small intestinal epithelium.

Characterization of the Human Colon Carcinoma Cell Line (Caco-2) as a Model System for Intestinal Epithelial Permeability

Caco-2 cells develop morphologic characteristics of normal enterocytes when grown on plastic dishes or nitrocellulose filters. The purpose of this study was to determine whether Caco-2 cells undergo similar differentiation when grown on Transwell polycarbonate membranes, and to study the suitability of Caco-2 monolayers as an intestinal epithelial transport model system. Transepithelial electrical resistance values after confluence were 173.5 omega.cm2 and remained unchanged through day 17. Permeabilities to the water-soluble fluid-phase markers that do not permeate the membrane, Lucifer yellow CH, [14C]inulin, [14C]polyethylene glycol, and [3H] dextran were less than 0.25% of the administered amount per hour after day 10. Qualitative evaluation of uptake and permeability to horseradish peroxidase confirmed the similarity in uptake and barrier properties between this cell system and the small intestinal epithelial layer. We conclude that Caco-2 cells grown on collagen-coated polycarbonate membranes should represent a valuable transport model system for the small intestinal epithelium.