Glycerol Transport Research Articles

Sensitivity analysis and parameter identification of nonlinear hybrid systems for glycerol transport mechanisms in continuous culture

In this paper, we establish a modified fourteen-dimensional nonlinear hybrid dynamic system with genetic regulation to describe the microbial continuous culture, in which we consider that there are three possible ways for glycerol to pass the cell's membrane and one way for 1,3-PD (passive diffusion and active transport). Then we discuss the existence, uniqueness, continuous dependence of solutions and the compactness of the solution set. We construct a global sensitivity analysis approach to reduce the number of kinetic parameters. In order to infer the most reasonable transport mechanism of glycerol, we propose a parameter identification model aiming at identifying the parameter with higher sensitivity and transport of glycerol, which takes the robustness index of the intracellular substance together with the relative error between the experimental data and the computational values of the extracellular substance as a performance index. Finally, a parallel algorithm is applied to find the optimal transport of glycerol and parameters.

Functional Characteristics of Aquaporin 7 as a Facilitative Glycerol Carrier

Aquaglyceroporins, which constitute a subgroup of aquaporin (AQP) water channels, had been believed to serve as channels for glycerol as well as for water. However, our recent studies have indicated that AQP9 and AQP10 operate in a carrier mode, which is of saturable nature, for glycerol transport. Assuming that such a functional characteristic could also be shared by AQP7, another aquaglyceroporin, we examined its glycerol transport function. The specific transport of glycerol by human AQP7, which was stably expressed in Madin-Darby canine kidney II cells, was indeed highly saturable, indicating the involvement of a carrier mode of operation mechanism. Kinetic analysis indicated that the specific transport conformed to Michaelis-Menten kinetics with the Michaelis constant of 11.9 µM and was not associated with a nonsaturable transport component as an indication of a simultaneous channel mode of operation, which was previously indicated for AQP10. AQP7-specific glycerol transport was furthermore found to be specifically inhibited by several compounds analogous to glycerol and operate without requiring either Na(+) or H(+). These characteristics of the carrier mode of AQP7 operation suggest that it is a facilitative carrier for glycerol and, possibly, also for analogous compounds, providing a novel insight into its operation mechanism.

Analysis of aquaporin 9 expression in human epidermis and cultured keratinocytes

Aquaporin 9 (AQP9) is a member of the aquaglyceroporin family that transports glycerol, urea and other small solutes as well as water. Compared to the expression and function in epidermal keratinocytes of AQP3, another aquaglyceroporin, our knowledge of epidermal AQP9 remains elusive. In this study, we investigated the expression of AQP9 in the human epidermis and cultured keratinocytes. Immunofluorescence studies revealed that AQP9 expression is highly restricted to the stratum granulosum of the human epidermis, where occludin is also expressed at the tight junctions. Interestingly, the AQP3 staining decreased sharply below the cell layers in which AQP9 is expressed. In cultured normal human epidermal keratinocytes (NHEK), knock-down of AQP9 expression in the differentiated cells induced by RNA interference reduced glycerol uptake, which was not as pronounced as was the case with AQP3 knock-down cells. In contrast, similar reduction of urea uptake was detected in AQP9 and AQP3 knock-down cells. These findings suggested that AQP9 expression in NHEK facilitates at least the transport of glycerol and urea. Finally, we analyzed the effect of retinoic acid (RA), a potent stimulator of keratinocyte proliferation, on AQP3 and AQP9 mRNA expression in differentiated NHEK. Stimulation with RA at 1μM for 24h augmented AQP3 expression and down-regulated AQP9 expression. Collectively, these results indicate that AQP9 expression in epidermal keratinocytes is regulated in a different manner from that of AQP3.

Competitive Inhibition of AQP7-mediated Glycerol Transport by Glycerol Derivatives

Aquaporin 7 (AQP7) is an aquaglyceroporin that has recently been found to operate as a facilitative carrier rather than a channel for glycerol, although its primary function is as a water channel. To probe into its substrate specificity, we examined the inhibitory effect of a series of acyl glycerol derivatives on glycerol transport mediated by human AQP7 stably expressed in Madin-Darby canine kidney II cells. According to kinetic analyses, AQP7-mediated glycerol transport was found to be competitively inhibited by monoacetin, monobutyrin and diacetin. Therefore, it may be possible that they all could be recognized as substrates by AQP7. The inhibition constant (Ki) of monoacetin (134 µM) was smaller than that of diacetin (420 µM), but greater than the Michaelis constant for glycerol (11.8 µM). Considering another finding that inhibition by triacetin was insignificant, it is likely that a decrease in the number of hydroxyl groups in the glycerol molecule by acetyl derivatization leads to a decrease in affinity for AQP7. The Ki of monobutyrin (80 µM) was, on the other hand, comparable with that of monoacetin, suggesting that the extension of the acyl chain by two hydrocarbon units does not have an impact on affinity for AQP7.

Urea transport mediated by aquaporin water channel proteins.

Aquaporins (AQPs) are a family of membrane water channels that basically function as regulators of intracellular and intercellular water flow. To date, thirteen aquaporins have been characterized. They are distributed wildly in specific cell types in multiple organs and tissues. Each AQP channel consists of six membrane-spanning alpha-helices that have a central water-transporting pore. Four AQP monomers assemble to form tetramers, which are the functional units in the membrane. Some of AQPs also transport urea, glycerol, ammonia, hydrogen peroxide, and gas molecules. AQP-mediated osmotic water transport across epithelial plasma membranes facilitates transcellular fluid transport and thus water reabsorption. AQP-mediated urea and glycerol transport is involved in energy metabolism and epidermal hydration. AQP-mediated CO2 and NH3 transport across membrane maintains intracellular acid-base homeostasis. AQPs are also involved in the pathophysiology of a wide range of human diseases (including water disbalance in kidney and brain, neuroinflammatory disease, obesity, and cancer). Further work is required to determine whether aquaporins are viable therapeutic targets or reliable diagnostic and prognostic biomarkers.

Expression and Localization of Aqua-glyceroporins AQP3 and AQP9 in Rat Oral Epithelia

Aquaporins (AQPs) are a family of small integral membrane proteins made up of 6 hydrophobic, a-helical, membrane-spanning domains surrounding a highly selective aqueous pore. AQP3, AQP7, and AQP9, termed aqua-glyceroporins, are known to be involved in the transport of water, glycerol, and other small molecules. In this study, we investigated the expression and localization of aqua-glyceroporins in rat oral stratified squamous epithelia of the palate, the buccal mucosa, the inferior aspect of the tongue, and the oral floor by using RT-PCR, immunofluorescence, and immunogold electron microscopy. AQP3 and AQP9 mRNAs were expressed in whole oral epithelium. Immunostaining for AQP3 was recognized in each type of epithelium. The results suggest that AQP3 synthesis begins predominantly in the cytoplasm of the basal cells. During the process of epithelial cell differentiation, AQP3 protein appears to accumulate and be transported to the plasma membrane, from where it is incorporated into the cornified or surface layers. The intracellular localization of AQP3 appears to correlate with the differentiation of keratinocytes, suggesting that it acts as an enhancer of the physiological permeability barrier together with membrane coating granules. The distribution pattern of AQP9 was limited to the marginal areas of the basal and suprabasal layers, which was different from that of AQP3. This difference in distribution between AQP3 and AQP9 suggests that AQP9 in rat oral epithelia acts as a channel by facilitating glycerol uptake from the blood through the endothelial cells of the capillary vessels to the oral stratified squamous epithelium. AQP3 and AQP9 facilitate both transcellular osmotic water flow and glycerol transport as pore-like passive transporters in the keratinocytes of oral epithelia, and may play a key role in not only hydration and the permeability barrier, but also cell proliferation, differentiation, migration, development, and wound healing by generating ATP.

Rhipicephalus ( Boophilus ) microplus aquaporin as an effective vaccine antigen to protect against cattle tick infestations

Vaccination as a control method against the cattle tick, Rhipicephalus (Boophilus) microplus has been practiced since the introduction of two products in the mid-1990s. There is a need for a vaccine that could provide effective control of R. microplus in a more consistent fashion than existing products. During our transcriptome studies of R. microplus, several gene coding regions were discovered to encode proteins with significant amino acid similarity to aquaporins. A cDNA encoding an aquaporin from the cattle tick, Rhipicephalus microplus, was isolated from transcriptomic studies conducted on gut tissues dissected from fully engorged adult female R. microplus. Bioinformatic analysis indicates this aquaporin, designated RmAQP1, shows greatest amino acid similarity to the human aquaporin 7 family. Members of this family of water-conducting channels can also facilitate the transport of glycerol in addition to water. The efficacy of this aquaporin as an antigen against the cattle tick was explored in cattle vaccine trials conducted in Brazil. A cDNA encoding a significant portion of RmAQP1 was expressed as a recombinant protein in Pichia pastoris, purified under native conditions using a polyhistidine C-terminus tag and nickel affinity chromatography, emulsified with Montanide adjuvant, and cattle vaccinated intramuscularly. The recombinant protein provided 75% and 68% efficacy in two cattle pen trials conducted in Campo Grande, Brazil on groups of 6 one year old Holstein calves. The effectiveness of this vaccine in reducing the numbers of adult female ticks shows this aquaporin antigen holds promise as an active ingredient in cattle vaccines targeted against infestations of R. microplus.

Biophysical Assessment of Human Aquaporin-7 as a Water and Glycerol Channel in 3T3-L1 Adipocytes

The plasma membrane aquaporin-7 (AQP7) has been shown to be expressed in adipose tissue and its role in glycerol release/uptake in adipocytes has been postulated and correlated with obesity onset. However, some studies have contradicted this view. Based on this situation, we have re-assessed the precise localization of AQP7 in adipose tissue and analyzed its function as a water and/or glycerol channel in adipose cells. Fractionation of mice adipose tissue revealed that AQP7 is located in both adipose and stromal vascular fractions. Moreover, AQP7 was the only aquaglyceroporin expressed in adipose tissue and in 3T3-L1 adipocytes. By overexpressing the human AQP7 in 3T3-L1 adipocytes it was possible to ascertain its role as a water and glycerol channel in a gain-of-function scenario. AQP7 expression had no effect in equilibrium cell volume but AQP7 loss of function correlated with higher triglyceride content. Furthermore it is also reported for the first time a negative correlation between water permeability and the cell non-osmotic volume supporting the observation that AQP7 depleted cells are more prone to lipid accumulation. Additionally, the strong positive correlation between the rates of water and glycerol transport highlights the role of AQP7 as both a water and a glycerol channel and reflects its expression levels in cells. In all, our results clearly document a direct involvement of AQP7 in water and glycerol transport, as well as in triglyceride content in adipocytes.

MAPK Hog1 closes the S. cerevisiae glycerol channel Fps1 by phosphorylating and displacing its positive regulators

The aquaglyceroprin Fps1 is responsible for glycerol transport in yeast in response to changes in extracellular osmolarity. Control of Fps1 channel activity in response to hyperosmotic shock involves a redundant pair of regulators, Rgc1 (regulator of the glycerol channel 1) and Rgc2, and the MAPK Hog1 (high-osmolarity glycerol response 1). However, the mechanism by which these factors influence channel activity is unknown. We show that Rgc2 maintains Fps1 in the open channel state in the absence of osmotic stress by binding to its C-terminal cytoplasmic domain. This interaction involves a tripartite pleckstrin homology (PH) domain within Rgc2 and a partial PH domain within Fps1. Activation of Hog1 in response to hyperosmotic shock induces the rapid eviction of Rgc2 from Fps1 and consequent channel closure. Hog1 was recruited to the N-terminal cytoplasmic domain of Fps1, which it uses as a platform from which to multiply phosphorylate Rgc2. Thus, these results reveal the mechanism by which Hog1 regulates Fps1 in response to hyperosmotic shock.

Are the basal cells of the mammalian epididymis still an enigma?

Basal cells are present in the columnar pseudostratified epithelium covering the epididymis of all mammalian species, which regulates the microenvironment where the functionally incompetent germ cells produced by the testis are matured and stored. Striking novelties have come from investigations on epididymal basal cells in the past 30-40 years. In addition to an earlier hypothesised scavenger role for basal cells, linked to their proven extratubular origin and the expression of macrophage antigens, basal cells have been shown to be involved in cell-cell cross-talk, as well as functioning as luminal sensors to regulate the activity of principal and clear cells. Involvement of basal cells in the regulation of electrolyte and water transport by principal cells was hypothesised. This control is suggested to be mediated by the local formation of prostaglandins. Members of the aquaporin (AQP) and/or aquaglyceroporin family (AQP3, AQP7 and AQP8) are also specifically expressed in the rat epididymal basal cells. Transport of glycerol and glycerylphosphorylcholine from the epithelium of the epididymis to the lumen in relation to sperm maturation may be mediated by AQP. Most probably basal cells collaborate to the building up of the blood-epididymis barrier through cell adhesion molecules, implying an involvement in immune control exerted towards sperm cells, which are foreigners in the environment in which they were produced.

Torulopsis versatilisstrains with increased salt tolerance carry mutations in the glycerol transporter geneFPS1

The salt-tolerant Torulopsis versatilis mutant strain, T3-5, is able to grow in YPD medium containing 22% salt, whereas the original strain, T, used for soy sauce fermentation was only able to grow in the presence of 20% or less. Biochemical analyses showed that strain T3-5 had a 22% higher intracellular glycerol level than T. Sequencing of the glycerol transporter gene FPS1 revealed a change from G to A at position 198 upstream of the start codon, changes from G to A at positions 93 and 1084, respectively, within the FPS1 gene, and insertions of T base at positions 285 and 310, respectively, downstream of the termination codon when comparing the corresponding sequences of strains T and T3-5. An inverse relationship between osmotic pressure and the FPS1 transcription level was observed for both T and T3-5 using qPCR. Therefore, it is possible that lower transcription levels of FPS1 are at least partly responsible for increased osmotolerance in strain T3-5. Overexpression of T and T3-5 FPS1 in Saccharomyces cerevisiae resulted in lower salt tolerance, especially in the presence of 12% salt. The data suggest that decreased expression levels of and/or alteration in the FPS1 protein contributed to increased salt tolerance of T3-5.

Analysis of osmoadaptation system in budding yeast suggests that regulated degradation of glycerol synthesis enzyme is key to near-perfect adaptation.

In order to maintain its turgor pressure at a desired homeostatic level, budding yeast, Saccharomyces cerevisiae responds to the external variation of the osmotic pressure by varying its internal osmotic pressure through regulation of synthesis and transport of the intracellular glycerol. Hog1PP (dually phosphorylated Hog1), a final effector in the signalling pathway of the hyper osmotic stress, regulates the glycerol synthesis both at transcriptional and non-transcriptional stages. It is known that for a step-change in salt concentration leading to moderate osmotic shock, Hog1PP activity shows a transient response before it returns to the vicinity of pre-stimulus level. It is believed that an integrating process in a negative feedback loop can be a design strategy to yield such an adaptive response. Several negative feedback loops have been identified in the osmoadaptation system in yeast. However, the precise location of the integrating process in the osmoadaptation system which includes signalling, gene regulation, metabolism and biophysical modules is unclear. To address this issue, we developed a reduced model which captures various experimental observations of the osmoadaptation behaviour of wild type and mutant strains. Dynamic simulations and steady state analysis suggested that known information about the osmoadaptation system of budding yeast does not necessarily give a perfect integrating process through the known feedback loops of Hog1PP. On the other hand, regulation of glycerol synthesising enzyme degradation can result in a near integrating process leading to a near-perfect adaptation.

Butanol production from glycerol by recombinant Escherichia coli

Escherichia coli MG1655 (DE3) with the ability to synthesize butanol from glycerol was constructed by metabolic engineering. The genes thil, adhe2, bcs operon (crt, bcd, etfB, etfA, and hbd) were cloned into the plasmid vectors, pETDuet-1 and pACYCDuet-1, then the two resulting plasmids, pACYC-thl-bcs and pET-adhe2, were transferred to E. coli, and the recombinant strain was able to synthesize up to 18.5 mg/L butanol on a glycerol-containing medium. After the glycerol transport protein gene GlpF was expressed, the butanol production was improved to 22.7 mg/L. The competing pathway of byproducts, such as ethanol, succinate, and lactate, was subsequently deleted to improve the 1-butanol production to 97.9 mg/L. Moreover, a NADH regeneration system was introduced into the E. coli, and finally a 154.0 mg/L butanol titer was achieved in a laboratory-scale shake-flask experiment.

Analysis of Salt-Tolerance Genes in Zygosaccharomyces rouxii

Zygosaccharomyces rouxii was mostly used in high-salt liquid fermentation of soy sauce. To better understand the osmo-adaption mechanism, two key salt-tolerance genes GPD1 coding for glycerol-3-phosphate dehydrogenase and FPS1 coding for a putative glycerol transporter were evaluated in the wild-type Z. rouxii (S) and a higher salt-tolerant mutant strain Z. rouxii 3-2 (S3-2) previously constructed. It was found that several mutations occurred in ZrGPD1 and ZrFPS1 in S3-2 compared with the control strain S. The mutation of ZrGPD1 in S3-2 resulted in the increase of transcription level of ZrGPD1 compared with the control. At the same time, the mutation of ZrFPS1 resulted in the decrease of transcription level of ZrFPS1. In addition, overexpression of S3-2GPD1 and S3-2FPS1 in Saccharomyces cerevisiae could cause the stronger salt tolerance compared to SGPD1 and SFPS1, respectively. The results suggested the improvement of salt tolerance in S3-2 was due to the increase of glycerol contents, which was resulted from the increase of transcription level of ZrGPD1 and the decrease of transcription level of ZrFPS1.

Comparative meta-RNA-seq of the vaginal microbiota and differential expression by Lactobacillus iners in health and dysbiosis

BackgroundBacterial vaginosis (BV), the most common vaginal condition of reproductive-aged women, is associated with a highly diverse and heterogeneous microbiota. Here we present a proof-of-principle analysis to uncover the function of the microbiota using meta-RNA-seq to uncover genes and pathways that potentially differentiate healthy vaginal microbial communities from those in the dysbiotic state of bacterial vaginosis (BV).ResultsThe predominant organism, Lactobacillus iners, was present in both conditions and showed a differing expression profile in BV compared to healthy. Despite its minimal genome, L. iners differentially expressed over 10% of its gene complement. Notably, in a BV environment L. iners increased expression of a cholesterol-dependent cytolysin, and of mucin and glycerol transport and related metabolic enzymes. Genes belonging to a CRISPR system were greatly upregulated suggesting that bacteriophage influence the community. Reflective of L. iners, the bacterial community as a whole demonstrated a preference for glycogen and glycerol as carbon sources under BV conditions. The predicted end-products of metabolism under BV conditions include an abundance of succinate and other short-chain fatty-acids, while healthy conditions are predicted to largely contain lactic acid.ConclusionsOur study underscores the importance of understanding the functional activity of the bacterial community in addition to characterizing the population structure when investigating the human microbiome.

Expression and functional studies of genes involved in transport and metabolism of glycerol in Pachysolen tannophilus

BackgroundPachysolen tannophilus is a non-conventional yeast, which can metabolize many of the carbon sources found in low cost feedstocks including glycerol and xylose. The xylose utilisation pathways have been extensively studied in this organism. However, the mechanism behind glycerol metabolism is poorly understood. Using the recently published genome sequence of P. tannophilus CBS4044, we searched for genes with functions in glycerol transport and metabolism by performing a BLAST search using the sequences of the relevant genes from Saccharomyces cerevisiae as queries.ResultsQuantitative real-time PCR was performed to unveil the expression patterns of these genes during growth of P. tannophilus on glycerol and glucose as sole carbon sources. The genes predicted to be involved in glycerol transport in P. tannophilus were expressed in S. cerevisiae to validate their function. The S. cerevisiae strains transformed with heterologous genes showed improved growth and glycerol consumption rates with glycerol as the sole carbon source.ConclusionsP. tannophilus has characteristics relevant for a microbial cell factory to be applied in a biorefinery setting, i.e. its ability to utilise the carbon sources such as xylose and glycerol. However, the strain is not currently amenable to genetic modification and transformation. Heterologous expression of the glycerol transporters from P. tannophilus, which has a relatively high growth rate on glycerol, could be used as an approach for improving the efficiency of glycerol assimilation in other well characterized and applied cell factories such as S. cerevisiae.

Diabetes and Infections-Hepatitis C: Is There Type 2 Diabetes Excess in Hepatitis C Infection?

Individual epidemiologic studies as well as the pooled analysis of observational studies have indicated the association between type 2 diabetes (T2D) and hepatitis C virus infection (HCV). Whether HCV infection is the cause of diabetes or diabetic patients are more prone to get HCV infection is still in question. The objective of the present review was to provide answers to this issue, based on available evidence from epidemiologic, molecular, experimental and therapeutic studies. Our current understanding of how chronic HCV infection could induce T2D is incomplete, but it seems twofold based on both direct and indirect roles of the virus. HCV may directly induce insulin resistance (IR) through its proteins. HCV core protein was shown to stimulate suppressor of cytokine signaling, resulting in ubiquitination and degradation of tyrosine kinase phosphorylated insulin receptor substrates (IRS1/2) in proteasomes. HCV-nonstructural protein could increase protein phosphatase 2A which has been shown to inactivate the key enzyme Akt by dephosphorylating it. Insulin signaling defects in hepatic IRS-1 tyrosine phosphorylation and PI3-kinase association/activation may contribute to IR, which leads to the development of T2D in patients with HCV infection. The peroxisome proliferator-activated receptors (PPARs) are also implicated. PPARα/γ, together with their obligate partner RXR, are the main nuclear receptors expressed in the liver. PPARα upregulates glycerol-3-phosphate dehydrogenase, glycerol kinase, and glycerol transport proteins, which allows for glucose synthesis during fasting states. Decreased activity of PPARs could attribute to HCV-induced IR. Immune-mediated mechanisms may be involved in the indirect role of HCV in inducing IR. It is speculated that TNF-alpha plays a major role in the pathogenesis of IR through lowering IRS1/2. Furthermore, HCV infection- triggered ER stress could lead to the activation of PP2A, which inhibits both Akt and the AMP-activated kinase, the regulators of gluconeogenesis. In summary, we illustrate that HCV infection is accompanied by multiple defects in the upstream insulin signaling pathway in the liver that may contribute to the observed prevalence of IR and diabetes. Future studies are needed to resolve this issue.

Protective role of AQP3 in UVA-induced NHSFs apoptosis via Bcl2 up-regulation

Aquaporin-3 (AQP3), a water/glycerol-transporting protein that facilitates water, urea, and glycerol transport, can inhibit arsenite-induced apoptosis by up-regulating Bcl-2. However, whether it has a protective role in ultraviolet A (UVA)-induced apoptosis in normal human skin fibroblasts is not known. In this study, we demonstrate that mild UVA treatment fails to induce oxidative cell stress and apoptosis in normal human skin fibroblasts (NHSFs) overexpressing AQP3. After severe UVA irradiation, there was an increase in oxidative cell stress and apoptosis when AQP3 levels decreased. We also found that silencing AQP3 sensitized NHSFs to low-dose UVA. Overexpressing AQP3 was protective against high-dose UVA-induced oxidative stress and apoptosis. Besides, we observed that Bcl-2 may be involved in UVA-induced apoptosis. Our findings suggested that the water/glycerol-transporting protein AQP3 plays a role in resistance to UVA-induced apoptosis.

Implication of Glycerol and Phospholipid Transporters in Mycoplasma pneumoniae Growth and Virulence

Mycoplasma pneumoniae, the causative agent of atypical pneumonia, is one of the bacteria with the smallest genomes that are nonetheless capable of independent life. Because of their longstanding close association with their human host, the bacteria have undergone reductive evolution and lost most biosynthetic abilities. Therefore, they depend on nutrients provided by the host that have to be taken up by the cell. Indeed, M. pneumoniae has a large set of hitherto unexplored transporters and lipoproteins that may be implicated in transport processes. Together, these proteins account for about 17% of the protein complement of M. pneumoniae. In the natural habitat of M. pneumoniae, human lung epithelial surfaces, phospholipids are the major available carbon source. Thus, the uptake and utilization of glycerol and glycerophosphodiesters that are generated by the activity of lipases are important for the nutrition of M. pneumoniae in its common habitat. In this study, we have investigated the roles of several potential transport proteins and lipoproteins in the utilization of glycerol and glycerophosphodiesters. On the basis of experiments with the corresponding mutant strains, our results demonstrate that the newly identified GlpU transport protein (MPN421) is responsible for the uptake of the glycerophosphodiester glycerophosphocholine, which is then intracellularly cleaved to glycerol-3-phosphate and choline. In addition, the proteins MPN076 and MPN077 are accessory factors in glycerophosphocholine uptake. Moreover, the lipoproteins MPN133 and MPN284 are essential for the uptake of glycerol. Our data suggest that they may act as binding proteins for glycerol and deliver glycerol molecules to the glycerol facilitator GlpF.

Expression of Aquaporin-3 in Ipsilateral Rat Kidney With Unilateral Partial Ureteral Obstruction

PurposeAquaporin (AQP), a protein located in the cellular membrane, allows rapid passage of water across the cell membrane. Various AQP subtypes have been associated with ureteral obstruction. In particular, AQP3 has two functions: water and glycerol transport. The aim of this study was to investigate the expression of AQP3 in the ipsilateral rat kidney in unilateral partial ureteral obstruction (UPUO).Materials and MethodsSprague-Dawley rats (n=30, 200-250 g) were divided into two groups. A sham operation was performed in the control group (n=10) and UPUO of the left upper ureter with a silicone tube was induced in the UPUO group (n=20). The left kidney was obtained from both groups 7 days after the operations. The kidney specimens underwent immunofluorescent staining with AQP3 monoclonal antibody, and the density of AQP3 in the tissue was measured with an image analyzer.ResultsIn the UPUO group, thinning of the epithelial layer and infiltration of inflammatory cells was seen along with the localized expression of AQP3 in the basolateral aspect of the principal collecting duct cells. The mean optical density of AQP3 was significantly lower in the UPUO group than in the control group (100.9±17.5 compared with 131.7±16.9; p<0.001).ConclusionsThese results suggest that a decrease in the expression of AQP3 may be the result of a urinary stasis reaction caused by UPUO in response to local and intrarenal factors. These changes suggest that AQP3 may have a pathophysiological role in UPUO.