Na+ Reabsorption in Cultured Rat Epididymal Epithelium via the Na+/Nucleoside Cotransporter1

Leung, George Pak-Heng; Cheung, King‐Ho; Tse, Chung Ming; Wong, Patrick

doi:10.1095/biolreprod64.3.764

Cited by 8 publications

(4 citation statements)

References 31 publications

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“…The relative importance of ADA1 and CNTs on nasal and bronchial epithelia was determined by comparing the effects of optimal concentrations of EHNA () (10 μM; Figure B) and phloridzin ( − ) (2 mM; Figure B) on the elimination of ASL adenosine over a concentration range including basal ( 5 , 72 , 73 ) and pathological (>100 μM) ( , ) conditions. We showed that ADA1 and CNT activities account for 40% and 60% of the elimination of a physiological (1 μM) adenosine concentration on nasal epithelia.…”

Section: Discussionmentioning

confidence: 99%

“…The contribution of paracellular diffusion was tested in Ussing chambers by comparing the permeability coefficients of adenosine and mannitol. The functional expression of CNTs and ENTs was investigated by use of the broad-range inhibitors phloridzin ( − ) and dipyridamole ( , ), respectively. The CNT isoforms were identified by competition assays, kinetic properties, and mRNA expression.…”

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confidence: 99%

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Adenosine Deaminase 1 and Concentrative Nucleoside Transporters 2 and 3 Regulate Adenosine on the Apical Surface of Human Airway Epithelia: Implications for Inflammatory Lung Diseases

et al. 2007

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Adenosine is a multifaceted signaling molecule mediating key aspects of innate and immune lung defenses. However, abnormally high airway adenosine levels exacerbate inflammatory lung diseases. This study identifies the mechanisms regulating adenosine elimination from the apical surface of human airway epithelia. Experiments conducted on polarized primary cultures of nasal and bronchial epithelial cells showed that extracellular adenosine is eliminated by surface metabolism and cellular uptake. The conversion of adenosine to inosine was completely inhibited by the adenosine deaminase 1 (ADA1) inhibitor erythro-9-(2-hydroxy-3-nonyl)adenine (EHNA). The reaction exhibited Km and Vmax values of 24 microM and 0.14 nmol x min(-1) x cm(-2). ADA1 (not ADA2) mRNA was detected in human airway epithelia. The adenosine/mannitol permeability coefficient ratio (18/1) indicated a minor contribution of paracellular absorption. Adenosine uptake was Na+-dependent and was inhibited by the concentrative nucleoside transporter (CNT) blocker phloridzin but not by the equilibrative nucleoside transporter (ENT) blocker dipyridamole. Apparent Km and Vmax values were 17 microM and 7.2 nmol x min(-1) x cm(-2), and transport selectivity was adenosine = inosine = uridine > guanosine = cytidine > thymidine. CNT3 mRNA was detected throughout the airways, while CNT2 was restricted to nasal epithelia. Inhibition of adenosine elimination by EHNA or phloridzin raised apical adenosine levels by >3-fold and stimulated IL-13 and MCP-1 secretion by 6-fold. These responses were reproduced by the adenosine receptor agonist 5'-(N-ethylcarboxamido)adenosine (NECA) and blocked by the adenosine receptor antagonist, 8-(p-sulfophenyl) theophylline (8-SPT). This study shows that adenosine elimination on human airway epithelia is mediated by ADA1, CNT2, and CNT3, which constitute important regulators of adenosine-mediated inflammation.

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Section: Discussionmentioning

confidence: 99%

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confidence: 99%

Adenosine Deaminase 1 and Concentrative Nucleoside Transporters 2 and 3 Regulate Adenosine on the Apical Surface of Human Airway Epithelia: Implications for Inflammatory Lung Diseases

et al. 2007

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“…This Na + /nucleoside cotransporter has been cloned recently and only a few studies have been reported. However, a role for CNT2 has been suggested in sodium reabsorption over epididymal epithelium [15]. The upregulation of CNT2 is probably of importance for the uptake of nucleosides and sodium during cholera and related diarrhoeal diseases.…”

Section: Discussionmentioning

confidence: 99%

“…The absorbed sugars are then transported over the basolateral membrane by facilitative sugar transporters (GLUTs), whereas the reabsorbed Na + can be transported to the serosal side by an active Na + /K + ATPase [14]. In a similar manner, Na + is reabsorbed together with nucleosides via the concentrative nucleoside transporter 2 (CNT2) [15].…”

Section: Introductionmentioning

confidence: 99%

Cholera toxin induces expression of ion channels and carriers in rat small intestinal mucosa

Flach

Lange²,

Jennische

et al. 2004

FEBS Letters

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Cholera toxin causes cyclic adenosine monophosphate (cAMP)-induced electrolyte and water secretion in the small intestine. The toxin-induced change in gene expression in rat small intestine was evaluated with microarray technique and the results were con¢rmed by semiquantitative polymerase chain reaction (PCR). The transporter CNT2 for nucleosides was upregulated between 6 and 18 h after challenge, whereas the level of GLUT1 transporter for glucose became elevated at 6 h. Both changes probably facilitate uptake of these nutrients in the gut. At 18 h, the major chloride channel in the villus, ClC2, was upregulated. Aquaporin 8 was downregulated at 6 h and two mucin-producing genes were upregulated 18 h after toxin challenge. The expression was back to normal after 72 h, which is the turnover time for intestinal epithelial cells.

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Immortalized Epididymal Cell Lines From Transgenic Mice Overexpressing Temperature‐Sensitive Simian Virus 40 Large T‐Antigen Gene

ARAKI,

SUZUKI,

MATUSIK

et al. 2002

Journal of Andrology

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Epididymal epithelium is well known as a site of secretion of various proteins present in epididymal luminal fluid. Although there have been many reports of primary cultures of epididymal epithelial cells, their growth is limited over time. We have established immortalized epididymal epithelial cell lines from primary cultures of epididymal cells from transgenic mice harboring temperature‐sensitive simian virus 40 large T‐antigen gene in order to study the regulatory mechanisms of epididymal function, including specific factor secretion. These cell lines (PC1 from proximal caput; and DC1, DC2, and DC3 from distal caput) have been maintained for more than 1 year and show temperature‐dependent growth and expression of cytokeratin, a marker of epithelial cells. These cells express the androgen receptor as well as markers of the murine epididymal epithelium, PEB‐like protein (ie, phosphatidye ethanolamine binding protein), E‐RABP (ie, epididymal retinoic acid‐binding protein), and EP17 (ie, epididymal protein of 17 kd). The androgen‐regulated 5‐kilobase mE‐RABP promoter DNA fragment ligated to the neomycin‐resistant gene was used for stable transfection of DC1 cells. Because the mE‐RABP gene is specifically expressed in the distal caput, neomycin selection provides a pure population of epithelial cells from that segment. This neomycin‐resistant immortalized cell line from the distal caput was cultured for more than 6 months. Such immortalized cell lines should be valuable tools for studying the regulation of tissue‐specific gene expression, and may be used to identify one or more epididymal specific transcription factors involved in the expression of epididymal specific proteins.

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Na+ Reabsorption in Cultured Rat Epididymal Epithelium via the Na+/Nucleoside Cotransporter1

Cited by 8 publications

References 31 publications

Adenosine Deaminase 1 and Concentrative Nucleoside Transporters 2 and 3 Regulate Adenosine on the Apical Surface of Human Airway Epithelia: Implications for Inflammatory Lung Diseases

Adenosine Deaminase 1 and Concentrative Nucleoside Transporters 2 and 3 Regulate Adenosine on the Apical Surface of Human Airway Epithelia: Implications for Inflammatory Lung Diseases

Cholera toxin induces expression of ion channels and carriers in rat small intestinal mucosa

Immortalized Epididymal Cell Lines From Transgenic Mice Overexpressing Temperature‐Sensitive Simian Virus 40 Large T‐Antigen Gene

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