scholarly journals Differential compartmentalization of BMP4/NOGGIN requires NOGGIN trans-epithelial transport

2021 ◽  
Author(s):  
Tien Phan-Everson ◽  
Fred Etoc ◽  
Shu Li ◽  
Samuel Khodursky ◽  
Anna Yoney ◽  
...  
Keyword(s):  
Epithelial Transport

Effect of sinomenine on thein vitrointestinal epithelial transport of selected compounds

2009 ◽  
pp. n/a-n/a ◽  
Author(s):  
Zhilei Lu ◽  
Weiyang Chen ◽  
Alvaro Viljoen ◽  
Josias H. Hamman
Keyword(s):  
Epithelial Transport

scholarly journals Role of the extracellular cAMP-adenosine pathway in renal physiology

2001 ◽  
Vol 281 (4) ◽  
pp. F597-F612 ◽  
Author(s):  
Edwin K. Jackson ◽  
Raghvendra K. Dubey
Keyword(s):  
Adenosine Receptors ◽  
Epithelial Transport ◽  
Receptor Activation ◽  
Hormonal Control ◽  
Renal Physiology ◽  
Tight Coupling ◽  
Extracellular Adenosine ◽  
Mediated Effects ◽  
Extracellular Camp

Adenosine exerts physiologically significant receptor-mediated effects on renal function. For example, adenosine participates in the regulation of preglomerular and postglomerular vascular resistances, glomerular filtration rate, renin release, epithelial transport, intrarenal inflammation, and growth of mesangial and vascular smooth muscle cells. It is important, therefore, to understand the mechanisms that generate extracellular adenosine within the kidney. In addition to three “classic” pathways of adenosine biosynthesis, contemporary studies are revealing a novel mechanism for renal adenosine production termed the “extracellular cAMP-adenosine pathway.” The extracellular cAMP-adenosine pathway is defined as the egress of cAMP from cells during activation of adenylyl cyclase, followed by the extracellular conversion of cAMP to adenosine by the serial actions of ecto-phosphodiesterase and ecto-5′-nucleotidase. This mechanism of extracellular adenosine production may provide hormonal control of adenosine levels in the cell-surface biophase in which adenosine receptors reside. Tight coupling of the site of adenosine production to the site of adenosine receptors would permit a low-capacity mechanism of adenosine biosynthesis to have a large impact on adenosine receptor activation. The purposes of this review are to summarize the physiological roles of adenosine in the kidney; to describe the classic pathways of renal adenosine biosynthesis; to review the evidence for the existence of the extracellular cAMP-adenosine pathway; and to describe possible physiological roles of the extracellular cAMP-adenosine pathway, with particular emphasis on the kidney.

scholarly journals Demonstration of the functional impact of vasopressin signaling in the thick ascending limb by a targeted transgenic rat approach

2016 ◽  
Vol 311 (2) ◽  
pp. F411-F423 ◽  
Author(s):  
Kerim Mutig ◽  
Tordis Borowski ◽  
Christin Boldt ◽  
Aljona Borschewski ◽  
Alexander Paliege ◽  
...  
Keyword(s):  
Epithelial Transport ◽  
Collecting Duct ◽  
Surface Expression ◽  
Urine Concentration ◽  
Dominant Negative ◽  
Transgenic Rat ◽  
Thick Ascending Limb ◽  
Water Reabsorption ◽  
Mediated Effects ◽  
Response To Water

The antidiuretic hormone vasopressin (AVP) regulates renal salt and water reabsorption along the distal nephron and collecting duct system. These effects are mediated by vasopressin 2 receptors (V2R) and release of intracellular Gs-mediated cAMP to activate epithelial transport proteins. Inactivating mutations in the V2R gene lead to the X-linked form of nephrogenic diabetes insipidus (NDI), which has chiefly been related with impaired aquaporin 2-mediated water reabsorption in the collecting ducts. Previous work also suggested the AVP-V2R-mediated activation of Na+-K+-2Cl−-cotransporters (NKCC2) along the thick ascending limb (TAL) in the context of urine concentration, but its individual contribution to NDI or, more generally, to overall renal function was unclear. We hypothesized that V2R-mediated effects in TAL essentially determine its reabsorptive function. To test this, we reevaluated V2R expression. Basolateral membranes of medullary and cortical TAL were clearly stained, whereas cells of the macula densa were unreactive. A dominant-negative, NDI-causing truncated V2R mutant (Ni3-Glu242stop) was then introduced into the rat genome under control of the Tamm-Horsfall protein promoter to cause a tissue-specific AVP-signaling defect exclusively in TAL. Resulting Ni3-V2R transgenic rats revealed decreased basolateral but increased intracellular V2R signal in TAL epithelia, suggesting impaired trafficking of the receptor. Rats displayed significant baseline polyuria, failure to concentrate the urine in response to water deprivation, and hypercalciuria. NKCC2 abundance, phosphorylation, and surface expression were markedly decreased. In summary, these data indicate that suppression of AVP-V2R signaling in TAL causes major impairment in renal fluid and electrolyte handling. Our results may have clinical implications.

Guanylin: a peptide regulator of epithelial transport 1

1995 ◽  
Vol 9 (8) ◽  
pp. 643-650 ◽  
Author(s):  
Leonard R. Forte ◽  
Mark G. Currie
Keyword(s):  
Epithelial Transport

Electrophysiology of plasma membrane vesicles

1984 ◽  
Vol 246 (4) ◽  
pp. F363-F372
Author(s):  
E. M. Wright
Keyword(s):  
Brush Border ◽  
Epithelial Transport ◽  
Electrical Potential ◽  
Membrane Vesicles ◽  
Tracer Uptake ◽  
Plasma Membrane Vesicles ◽  
Experimental Conditions ◽  
Optical Signals ◽  
Brush Border Membranes ◽  
Vesicle Preparation

In both renal and gastrointestinal physiology, it has become popular to study epithelial transport phenomena using vesicles isolated from the apical and basolateral cell membranes. Transport in vesicle preparations is usually monitored with radioactive tracers, but more recently attention has been directed to electrophysiological methods. As it is impossible to measure the electrical properties of membranes in small vesicles (less than 500 nm diam) with classical electrophysiological techniques, indirect methods have to be employed. In this review I focus on the application of voltage-sensitive optical probes to measure membrane potentials in brush border membrane vesicles. Optical signals are calibrated with diffusion potentials generated with known ion gradients in the presence of ionophores, e.g., EKS with K gradients in the presence of valinomycin. Membrane potential measurements can be used 1) to illustrate the specificity and kinetics of sugar-, amino acid-, and carboxylic acid-Na cotransport systems in brush border membranes, and 2) to determine the ion permeability of brush border membranes. All organic solutes known to be transported by Na cotransport across brush border membranes depolarize the membrane in a Na-dependent, saturable manner. The results agree, both qualitatively and quantitatively, with electrophysiological data obtained in the intact renal tubule and with tracer uptake in vesicles. Bi-ionic potential measurements demonstrate that brush border membranes are permselective to anions and cations, but there are indications that the permeabilities are somewhat dependent on the method of vesicle preparation and the experimental conditions. However, electrical potential measurements provide insight into the mechanisms of ion transport in vesicle preparations, and the application of patch-clamp techniques should provide further gains in the future.

Comparison of a computer simulation program and a traditional laboratory practical class for teaching the principles of intestinal absorption.

1994 ◽  
Vol 267 (6) ◽  
pp. S95 ◽  
Author(s):  
D G Dewhurst ◽  
J Hardcastle ◽  
P T Hardcastle ◽  
E Stuart
Keyword(s):  
Undergraduate Students ◽  
Epithelial Transport ◽  
Undergraduate Curriculum ◽  
Computer Assisted ◽  
Knowledge Gain ◽  
Student Centered ◽  
Student Centered Learning ◽  
Before And After ◽  
Resource Requirements ◽  
Approach Working

Here we describe an evaluation of the effectiveness, compared with a traditional laboratory, of an interactive computer-assisted learning (CAL) program, which simulates a series of experiments performed using isolated, everted sacs of rat small intestine. The program is aimed at undergraduate students of physiology and is designed to offer an alternative student-centered learning approach to the traditional laboratory-based practical class. The evaluative study compared two groups of second-year undergraduate students studying a module on epithelial transport: one group worked independently using the CAL program and associated learning materials, and the other group followed a conventional practical class approach, working in the laboratory under supervision. Knowledge gain of each group was measured by means of a test consisting of a range of question types (e.g., short-answer factual, calculation, interpretation) given to students before and after the module. Student attitude to both approaches was assessed by questionnaire, and the resource requirements were also compared. It was found that the knowledge gain of both groups of students was the same, that students had a positive attitude toward using CAL programs of this type, and that the cost of the conventional laboratory-based approach was five times greater. The potential for integrating CAL programs into the undergraduate curriculum is discussed.

scholarly journals Epithelial Transport of Macromolecules: Gastric Mucous Exocytosis

MEMBRANE ◽  
2011 ◽  
Vol 36 (6) ◽  
pp. 286-292
Author(s):  
Takashi Nakahari ◽  
Yukinori Sawabe ◽  
Chikao Shimamoto
Keyword(s):  
Epithelial Transport ◽  
Gastric Mucous ◽  
Transport Of Macromolecules
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